Chapter II: Part 2

The precious or noble opal is found chiefly in the mines of Czernowitza, between Kaschau and Eperies, in Hungary, and in Gracias á Dios, a province in Honduras.

In olden times, the Greek and Turkish merchants carried opals from Hungary to the Orient, and then they were shipped to Holland and sold in Europe as Oriental opals.

The fire opal is of a yellowish-red color, and is found chiefly in Mexico, although it also occurs in Hungary, the Faroe Islands, Honduras, and Guatemala.

The common opal is found in Ireland, Denmark, Frankfurt, Guatemala, and South Australia, and also in Hungary and Mexico. These opals are translucent without fire or reflection.

The hydrophane is an opal that has lost color and brilliancy by reason of the evaporation of its water. If placed in water or alcohol, this stone becomes transparent, only to lose this quality when the water or alcohol has evaporated.

The hydrophane becomes transparent more quickly in warm than in cold water, but most rapidly in alcohol. If boiled in oil, the hydrophane is said to retain its brilliancy for years.

The cachelong is milky-white, and nearly opaque, and is found in small masses in the river Cach, in Bucharia, and also in Iceland.

Although one of the most magnificent of the gem stones, the opal for many years was under the ban of superstition. Now, this splendid stone once more commands a foremost place in the jewelers’ art, and the opal mines of Hungary and Queensland are being worked to their fullest extent to supply the demand.

PEARL.

Although an organic product, the pearl is always ranked amongst the most precious of gems, and is distinguished by being the only gem that does not require the lapidary’s touch to bring out its beauties.

Ancient writers have accounted for the origin of pearls by saying that they were formed of angels’ tears, or drops of dew from heaven, which, during the midsummer nights, fell into the gaping mouths of the pearl-oysters.

According to modern scientific investigation, the formation of the pearl does not seem to be the result of healthy natural causes, but comes from the efforts of the oyster to rid itself of some foreign substance, like a grain of sand, a bit of shell or vegetation, or some unwelcome visitor in the shape of a small water insect.

When annoyed by an intruding substance, the oyster begins to deposit its nacre, or mother-of-pearl, in regular concentric layers around the intruder, these layers gradually increasing in circumference and forming the pearl. Thus, like an onion, the pearl is merely a succession of layers or skins, starting from a small core, or nucleus, which is always present, though often only of microscopical size.

Pearls have sometimes been found where the outer layer, or skin, as it is technically called, has been discolored or otherwise injured, and when this top skin has been carefully removed the result was a somewhat smaller but perfect pearl.

This, however, is a very delicate operation, and at the pearling grounds is only resorted to by men of experience. The composition of the pearl is carbonate of lime, with a small proportion of organic matter, and the specific gravity 2.5 to 2.7.

The pearl is affected by acids, and is easily calcined on exposure to heat.

In color, the pure white, slightly transparent, is the most highly prized; while in India and China the bright yellow colors are sought after.

Decided colors, however, such as black, pink, and golden-yellow bring a high price, and, in fact, black pearls, if perfect in color and shape, are at present more valuable than any other kind.

The beauty and value of a pearl depend on form, quality of texture or skin, color, transparency or water, and lustre or orient.

In form, the perfectly round shape comes first in value, then a finely formed drop or pear shape, and lastly the oval or egg shape.

Pearls that are flat on one side and rounded on the other are called boutons or button pearls. These are frequently found attached to the shell, and are cut out and the bottom part smoothed and polished.

It is easy, however, to detect this class of pearls by the lack of pearly lustre on the side that was attached to the shell.

When a pearl is rough and odd-shaped it is called a baroque, and some extremely fantastic shapes are found, especially in fresh-water oysters.

The texture or skin of a fine pearl should be perfectly smooth and free from all spots, indentations, wrinkles, or scratches.

Pure white is the desirable color for a gem pearl, but many others that are slightly tinted with blue, pink, or yellow will pass for gems if they are otherwise perfect.

The transparency or “water” of a pearl, while not existing in fact, is still one of the requisites of a fine pearl; there must be an appearance of transparency, which adds to the beauty of the gem.

To describe the lustre or orient of the pearl, the author can only use the term pearly, as there is no other substance that approaches the brilliancy and color of a pearl, excepting, of course, mother-of-pearl—the nacre in the pearl-oyster.

Without orient or lustre, the pearl of finest form and color has but little value.

Lustre is to the pearl what brilliancy is to the diamond; when the orient is absent there is no life, no beauty.

Pearls are principally supplied by two groups of pearl-oysters or mussels: the marine or meleagrina margaritifera, a round-cornered square shell with very thick sides, measuring six to eight inches in length.

The color of this shell is mostly blackish-green, but it is also sometimes yellowish; the edges of the inner part of the shell are black, but the rest of the interior is the beautiful mother-of-pearl.

The oyster itself is small for the size of the shell.

This specimen is found on the coast of Ceylon, Persian Gulf, Japanese, Mexican and California coasts, the western shores of South America, Brazil, West Indian Islands, Panama, Sooloo Archipelago, and the northeast and northwestern coast of Australia.

The fresh-water or unio margaritifera is an even, egg-shaped mussel found in brooks, rivers, and lakes in temperate zones in nearly all parts of the world.

Some fine river pearls have been found in the United States, but most of the American pearls are of a button or elongated shape, or are baroques or fancy-shaped.

In China many people engage in the business of making small pellets of clay or metal images, which in the month of May are introduced into the river mussels (mytilus cygneus).

The mussels are replanted, and in November they are taken up again. Some of the oysters die, but most of them are found to have been actively at work covering the little pellets or metal figures with nacre, and while no strictly first-class pearls are formed in this way, many curious little pearl figures or gods are made and sold to the curious or devout.

Pink or conch pearls are found in the Gulf of California and coasts of Mexico, Bahama Islands, West Indian Islands, and in some rivers in South America.

They seldom occur in regular shapes, and although they are termed pink pearls, they range in color from red to pale yellow, and are often found of a china-white color.

The pink pearl displays a wavy appearance and a peculiar sheen, something like watered silk. As the pink pearl is seldom found perfectly round and of a good color, such a specimen is very valuable.

CHRYSOLITE.

The chrysolite, peridot, and olivine differ in color, but are practically of the same composition.

The chrysolite proper is of a pale greenish-yellow color, the peridot a deep olive-green, and the olivine of a yellowish or light olive-green color; these stones also shade into brown. They crystallize on the rhombic system, are transparent to translucent, 6.5 to 7. in the scale of hardness, and 3.3 to 3.5 in specific gravity.

The cleavage is distinct, fracture conchoidal, refraction double, and lustre vitreous, and in the olivines somewhat greasy.

These stones are easily affected by sulphuric acid, but are infusible before the blow-pipe, excepting some kinds containing much iron.

With borax, they melt to a pale-green transparent glass.

Chrysolites are composed of silica, magnesia, and oxide of iron.

Perfectly crystallized chrysolites are brought from Constantinople, but the exact locality where they are found is unknown.

Less distinct specimens occur at Vesuvius, Mexico, the isle of Bourbon, Auvergne, Egypt, Natolia, Brazil, Germany, Pegu, Ceylon, Switzerland, and North America.

Peridots are distinguished by being the only precious stones that have literally dropped from heaven, as they have been found in meteorites.

The Oriental chrysolite of commerce is true chrysoberyl, and is harder and heavier than chrysolite, and the stone called Ceylon chrysolite is a greenish-yellow tourmaline, which is easily distinguished, as it is also harder while considerably lighter than the chrysolite.

The green garnet is of a pronounced green color, and is harder and heavier than the olivine or chrysolite. Although suitable for mounting in brooches and other ornaments, these stones are not sufficiently hard for the rough usage as ring-stones.

GARNET.

Almandine, almandite, Syrian garnet, essonite, cinnamon-stone, pyrope, Bohemian garnet, vermeille, Cape garnet, Cape ruby, Arizona ruby, American ruby, carbuncle, uwarowite, demantoide, grossularite, and Bobrowska garnet are some of the scientific and commercial names for different species and colors of the garnet group.

The crystallization of the garnet is isometric, refraction single, specific gravity 3.15 to 4.3, hardness 5 to 8, lustre vitreous, fracture uneven, colors red, violet, brown, yellow, green, and white, and the various shadings of these colors.

Most varieties fuse easily to a brown or black glass; the uwarowite fuses with borax to a clear chrome-green glass.

Syrian, almandine, almandite, and carbuncle are different names for the iron-alumina garnet.

In colors, these stones shade from deep-red to violet and brownish-red, and are composed of:

Silica 36.01
Alumina 20.06
Protoxide of iron 43.03

The specific gravity is 4. to 4.2, and hardness 7.5.

This garnet, sometimes called the precious garnet, is found in Ceylon, Pegu, Brazil, Greenland, Hindustan, Bohemia, Tyrol, Œtzthal, Carinthia, Styria, Switzerland, Ariolo, Canaria, Maggia, Hungary, Sweden, Norway, Scotland, Spain, and the United States.

Grossularite, or lime-alumina garnet, is known in commerce as essonite, or cinnamon-stone. The color is yellow, of various shades; specific gravity 3.5 to 3.65, and hardness 6.5.

These stones are sometimes sold for jacinths, but they are softer than the jacinth, and melt easily before the blow-pipe. Essonites come principally from Ceylon, but are also found in other places.

Pyrope or Bohemian garnet is the magnesia-alumina variety, and is of a uniform dark blood-red color. This stone is found in Bohemia, and although quantities of small pieces are found, large specimens are rare, and a piece that will cut into a four- or five-carat stone is seldom met with and commands a high price.

These garnets are found at Stiefelburg by Meronitz, Triblitz, Podsedlitz, and Neupaka.

The pyrope turns black under the blow-pipe, then red again, and melts with difficulty into a black glass. With borax it melts to an emerald-green glass. The specific gravity of this garnet is 3.69 to 3.78, and hardness 7.5.

Vermeille is a name given to the orange-red almandine, Cape garnet to the bright red-yellow variety, Cape ruby to the pyrope, and American ruby to the blood-red kind found in New Mexico, Montana, and Arizona. Carbuncle is a term applied _to all_ garnets cut with a smooth rounding top, sometimes called, after the French, cabochon.

Uwarowite or lime-chrome garnet is one of the rarest and most beautiful of the garnet group.

The color of this stone is emerald-green, hardness 7.5, and specific gravity 3.41 to 3.52. Uwarowites are found near Bissersk in the Urals of Russia, but rarely in specimens of sufficient size to cut into gems.

This garnet is heavier and harder than the true emerald.

Demantoide or Bobrowska garnet is a soft garnet, olive-green to brown and blackish-green in color, sometimes light green. It is found in the Bobrowska River in the Urals. The specific gravity is 3.85, and hardness about 6, its softness making it undesirable for many ornaments. Before the blow-pipe it fuses into a black bead.

These garnets are often sold as olivines; they are heavier than olivines and softer.

Demantoide is composed of:

Silica 35.44
Lime 32.85
Sesquioxide of iron 32.85
Magnesia .20

TOPAZ.

Topaz belongs to the rhombic system of crystallization. Its cleavage is basal and perfect, fracture uneven, hardness 8, scratching quartz distinctly, specific gravity 3.4 to 3.6, lustre vitreous, refraction double, and colors ranging from colorless or white to bluish-white, light blue, wine-yellow, straw-yellow, golden-yellow, greenish- and pale-red to pink.

Topaz becomes electric from rubbing or pressure, and retains electricity for twenty-four hours. Before the blow-pipe topaz partly loses color, but does not melt, and with borax it fuses slowly to a white bead.

Topaz is partially attacked by sulphuric acid, and dissolves in salts of phosphorus.

The composition of topaz is:

Silicon 15.05
Aluminium 30.02
Oxygen 36.08
Fluorine 17.05

Goutte d’eau or colorless topaz, sometimes called “slaves diamond,” Siberian or bluish-white, Brazilian or golden to reddish-yellow, Saxony or pale-wine yellow, Brazilian ruby or pink, Brazilian sapphire or light blue, and aquamarine or greenish, are the various commercial names for topaz.

Most of the Brazilian rubies or pink topazes are produced by heating the reddish or dark-yellow variety, either in a crucible or by enveloping the stone in German tinder and setting fire to the tinder. If heated too much, the stone is apt to become colorless, and if suddenly cooled it may crack.

Colorless or white topaz takes a very high polish, and is wonderfully clear and transparent.

The great Portuguese diamond, “The Braganza,” of about 1,680 carats, is supposed to be a white topaz.

Topaz is found in the Urals, Kamschatka, Alabaschka, Miask, Nestschinsk, Adun Tschilon, Villa Rica, Boa Vista, Capao, Lana, Minas Novas, Cairngorm Mts., Schlackenwald, Zinnwald, Schneckenstein, Ehrenfriedensdorf, Altenburg, Orenburg, Mourne Mts.—Ireland, Australia, New South Wales, Ceylon, Mexico, and the United States. False topaz, or the ordinary topaz of commerce, is yellow quartz resembling yellow topaz, but lacking its brilliancy and hardness; it is also very much lighter, being only 2.5 to 2.7 in specific gravity.

Beryl and chrysolite are often mistaken for topaz, but as they are softer and beryl is much lighter, they are easily distinguished from the topaz. The strong electric property of the topaz is also a conclusive test.

Oriental topaz, or yellow corundum, is harder and heavier than the occidental or true topaz.

APATITE.

Apatite, which is seldom used as a gem stone, sometimes resembles the beryl and emerald, but is much softer and rarely has the color and brightness combined of the former gems.

This mineral, composed principally of subsesquiphosphate of lime, is 4.5 to 5. in hardness, has the specific gravity of 2.95 to 3.25, is transparent to opaque, vitreous in lustre, infusible before the blow-pipe, and dissolves slowly in nitric acid. In colors, apatite varies from colorless to sea-green, bluish-green, violet-blue, gray, yellow, red, and brown.

Apatite is found in Saxony, the Hartz Mts., Bohemia, Norway, Bavaria, England, St. Gothard in Switzerland, and in the United States.

FELSPAR.

Four varieties of felspar are used as gem stones—moonstone or orthoclase, sunstone or avanturine felspar, Amazon stone or green felspar, and Labrador or Labrador spar.

MOONSTONE.

This variety of felspar is called orthoclase, adularia, and orthose, besides the commercial names of fish-eye, Ceylon or water opal, and in the yellow and red tints sunstone. Moonstone occurs in crystals and crystalline fragments, also massive and granular; its hardness is 6. to 6.5, specific gravity 2.4 to 2.6, refraction double, is not attacked by acids, and is composed of:

Silica 64.5
Alumina 18.5
Potash 17.
With traces of soda.

This beautiful stone is the clearest of all varieties of felspar. It is colorless, or only slightly tinted with blue, green, yellow, and flesh-red, and is transparent to translucent.

The lustre is vitreous, and a brilliant pearly streak of white light plays from side to side.

The yellowish- and reddish-tinted specimens are called sunstones, and are quite rare. These sunstones must not be confounded with the avanturine or felspar sunstone.

Moonstones are found principally in Ceylon and on the St. Gothard in Switzerland, but also occur in Bavaria, Greenland, Tyrol, Dauphine, Norway, and the United States.

During the past few years, large quantities of moonstone balls, cut like whole pearls, have been used for jewelry—the stones being much sought as well because of their beauty as on the ground of the popular superstition that they will bring good luck to the wearer.

Small pieces or balls are not very valuable, but large perfect specimens command a good price.

SUNSTONE.

(AVANTURINE FELSPAR.)

Sunstone or avanturine felspar is a variety of oligoclase; grayish-white to reddish-gray in color, usually the latter; containing minute crystals of hematite, göthite or mica, which are imbedded and scattered through the stone, and give forth golden-yellow, reddish, or prismatic reflections. The hardness is 6 to 7, specific gravity 2.56 to 2.72, and lustre pearly or waxy to vitreous.

Sunstones are found near Stockholm, in Finland, the Urals, Ceylon, the Alps, Iceland, the United States, and other places.

AMAZON STONE.

(GREEN FELSPAR.)

The Amazon stone is a green variety of felspar, which was first found on the banks of the Amazon River, but now comes from Siberia and the United States. This stone consists of potash, alumina, and silex—is green in color but rarely clean, being discolored in places and usually covered with small white spots.

The Amazon stone is harder than glass, but is scratched by rock crystal. Its specific gravity is 2.5 to 2.6; acids do not affect it, and it melts with difficulty before the blow-pipe.

LABRADORITE.

Labrador stone or labradorite is sometimes known as opaline felspar, and was first discovered on the island of St. Paul on the coast of Labrador.

Labradorite is translucent to opaque, gray-green or brown in color, and has beautiful chatoyant reflections of brilliant blue, sea-green, and sometimes red and yellow, changing from one color to another. Labradorite is 6 in hardness, has a specific gravity of 2.62 to 2.76; a vitreous to pearly lustre, is brittle, fuses with difficulty before the blow-pipe, and is decomposed by muriatic acid. It is composed of:

Silica 52.9
Alumina 30.3
Lime 12.3
Soda 4.5

Large masses of this stone are found on the coast of Labrador. It is also found in Finland, Russia, and the United States. Because of the dark chatoyant appearance the name of œil de bœuf or ox-eye is sometimes applied to labradorite. Handsome specimens, cut cabochon, form pretty ring stones, and many effective engraved cameos have been produced by using the bright portion for the relief work and the gray dead part for the base.

CYANITE.

This stone is the transparent variety of disthene, and is sometimes commercially known as sappare. Cyanite is colorless to bluish-white, sky-blue, berlin blue, yellowish- and reddish-white, gray, and green.

The hardness is 5 to 7, specific gravity 3.45 to 3.70, lustre vitreous and pearly; it is infusible before the blow-pipe, but fuses with borax; is not attacked by acids, and is composed of:

Silica 36.8
Alumina 63.2

Cyanite is found in Switzerland, the Tyrol, Styria, Carinthia, Bohemia, Norway, Finland, France, South America, Scotland, Ireland, Siberia, the East Indies, and the United States. Clean specimens are not plentiful, and fine blue pieces have frequently been sold for sapphires. The cyanite can be distinguished from the sapphire by its inferior hardness and lighter weight.

LAPIS LAZULI.

Lapis lazuli, the sapphire of the ancients, is a mineral, translucent to opaque, ranging in color from colorless to an azure-blue, violet-blue, green, and red.

The principal color, however, is a rich, azure blue, sometimes shading into green, and having a vitreous to greasy lustre.

Its hardness is 5 to 5.5, specific gravity 2.38 to 2.42; it is decomposed by muriatic acid, and fuses before the blow-pipe to a white glass. It is rarely found clean, but has usually a number of veins and spots of a metallic nature. It is composed of:

Silica 45.
Alumina 31.76
Soda 9.09
Lime 3.52
Sulphuric acid 5.89
and traces of iron, soda, and potash.

This mineral is found in Siberia, Transylvania, Persia, China, Thibet, Tartary, South America, India, and Brazil.

Lapis lazuli is sometimes employed for jewelry, and was for some centuries ground up and used to make the mineral paint known as genuine ultramarine. This paint is now produced chemically, and the more costly mineral compound is rarely used.

The imitation of lapis lazuli for jewelry purposes is also very easy, as metal filings can be readily introduced into the azure blue glass, and thus an imitation of the genuine stone produced, which is perfect excepting in hardness.

HIDDENITE.

The hiddenite is a variety of spodumene that has only been found in one locality, namely, Alexander County, North Carolina. This mineral was discovered by W. E. Hidden, and has been named after him.

The hiddenite is perfectly transparent, and varies from a pale yellowish- to a deep emerald-green, being very brilliant, and approaching the emerald in color. As this stone is rarely found large enough for cutting into gems, it is highly prized, and good specimens command a large price.

The hardness of the hiddenite is 6.5 to 7, and specific gravity 3.13 to 3.19; before the blow-pipe it melts to a clear glass, and it is attacked by salts of phosphorus. It is composed of:

Silica 64.35
Alumina 26.58
Lithia 7.05
with traces of iron and soda.

SPODUMENE.

Spodumene is sometimes cut and polished as a gem, but its peculiar cleavage makes it a bad stone for the lapidary to cut and the jeweler to mount.

Its hardness is 6.5 to 7, specific gravity 3.13 to 3.19, and lustre, vitreous to pearly.

Grayish-green, greenish-white, and sometimes yellow or faint red are the colors. Its composition is:

Silica 64.2
Alumina 29.4
Lithia 6.4

Acids do not attack spodumene, and under the blow-pipe it fuses to a white glass.

This mineral is found in Sweden, the Tyrol, Ireland, Scotland, and the United States.

DICHROITE.

Dichroite is sometimes known under the mineralogical names of cordierite and iolite, and commercially as _saphir d’eau_, or water sapphire. This stone is remarkable for pleichroism, sometimes showing three different colors in as many directions, and when properly cut has often the star formation of the corundum star-stones.

Water sapphire, as the blue specimens are called, is 7 to 7.5 in hardness, specific gravity 2.56 to 2.67, transparent to translucent, and frequently full of flaws. It is partially decomposed by acids, melts with difficulty before the blow-pipe, is vitreous to greasy in lustre, and is composed of:

Silica 49.
Alumina 32.
Ferrous oxide 7.
Magnesia 9.

Besides the _saphir d’eau_, which is blue, dichroite occurs colorless, bluish-white, yellowish-white, yellowish-gray to yellowish-brown, indigo to blackish-blue, and violet. This mineral is found in Ceylon, Spain, Norway, Sweden, Tuscany, Greenland, and Bavaria. Sapphire is harder and much heavier than dichroite.

IDOCRASE.

Idocrase or vesuvianite was first found amongst the ancient ejections of Vesuvius, and it is still found at Vesuvius in hair-brown to olive-green colors.

Vesuvianite is 6.5 in hardness, 3.35 to 3.45 in specific gravity, transparent to opaque, lustre vitreous to greasy. It possesses strong double refraction, is attacked by acids, and melts readily under the blow-pipe. Vesuvianite consists of:

Silica 37.75
Alumina 17.23
Sesquioxide of iron 4.43
Magnesia 3.79
Lime 37.35

In colors, this mineral shades from brown to black, yellow, pale-blue, and green, and it is found at Vesuvius, Alps, Piedmont, Mt. Somma, Etna, Norway, Sweden, Spain, Hungary, Urals, and the United States.

Transparent or strongly translucent specimens, in handsome green or brown varieties, are used for jewelry, principally, however, in Turin and Naples.

Chrysolite and green garnet are sometimes substituted for vesuvianite. The first has a greater specific gravity and is more vivid in color, and the latter is also heavier and harder.

EUCLASE.

Euclase is very brittle, and therefore is rarely used as an ornamental stone.

This mineral has the hardness of 7.5; specific gravity, 3.1; lustre, vitreous to pearly; it is transparent to semi-transparent, doubly refractive, is not acted upon by acids, fuses under the blow-pipe to a white enamel, and is composed of:

Silica 41.2
Alumina 35.2
Glucina 17.4
Water 6.2

Euclase occurs in Brazil, in the neighborhood of Villa Rica, and also in the Urals, in colorless, pale green, blue, pale yellow, and white colors.

SPHENE.

Sphene or titanite is also a brittle mineral, 5 to 5.5 in hardness; specific gravity, 3.4 to 3.56; transparent, doubly refractive; lustre, adamantine to resinous; colors, brown, gray, yellow, green, black, and colorless; and composition:

Silica 31
Titanium oxide 41
Lime 27
Ferrous oxide 1

When transparent in colorless, greenish, or yellow colors, this mineral presents an appearance like the fire opal.

Sphene is found in Switzerland, the Urals, Tyrol, Finland, Wales, Ireland, Germany, Canada, and the United States.

PHENACITE.

This mineral, rarely used as a gem stone, is 7.5 to 8 in hardness; specific gravity, 2.96 to 3; lustre, vitreous; transparent to semi-translucent, doubly refractive, it does not melt before the blow-pipe, and contains:

Silica 54.2
Glucina 45.8

Phenacite occurs colorless, and also bright wine-yellow inclining to red, and brown. This stone is found in Russia, Mexico, and Alsace.

The colorless or transparent variety approaches the diamond in brilliancy, especially under artificial light.

EPIDOTE.

Epidote usually occurs in a peculiar yellowish-green, called pistachio green, a color that is seldom found in other minerals. Besides this color, olive, brownish-green, greenish-black and black, red, yellow-gray, and grayish-white occur. The hardness of epidote is 6 to 7; specific gravity, 3.32 to 3.50; lustre, vitreous to pearly; refraction, double. The stone is transparent to opaque, is attacked by acids, and is slightly affected by the blow-pipe. It is composed of:

Silica 38
Alumina 22
Ferric oxide 15
Lime 23
Water 2

Epidote is found in Norway, Saxony, Siberia, Brazil, on the St. Gothard, in Switzerland, in the Tyrol, and in the Hartz.

AXINITE.

Axinite is a brittle mineral which has occasionally furnished some pretty gem stones.

The hardness of this stone is 6.5 to 7; specific gravity, 3. to 3.3; lustre, vitreous. It is transparent to translucent, is not attacked by acids, and melts readily before blow-pipe. It is composed of:

Silica 43
Lime 20
Alumina 16
Ferric oxide 10
Boron trioxide 5
Manganese dioxide 3
Magnesia 2
Potash 1

Axinite occurs in clove-brown, plum-blue, and pearl-gray, and exhibits trichroism. The best specimens come from St. Christophe in Dauphiny, but it is also found at Santa Maria, and in Switzerland, Sweden, England, Chili, Saxony, the Hartz Mountains, and the United States.

Axinite is usually cut, like the opal, cabochon, but is rarely used as a gem stone.

DIOPSIDE.

Diopside is cut and sometimes sold in Turin and in Chamouny as a gem stone, but no great quantity of this mineral is used for ornamental purposes.

The hardness of diopside is 5 to 6; specific gravity, 2.9 to 3.5; lustre, vitreous to greasy. It is transparent to translucent, brittle, cannot be dissolved by acids, and melts before the blow-pipe. It is composed of:

Silica 54
Lime 24
Magnesia 18
Ferrous oxide 4

This mineral is grayish-white to pearl-gray, and greenish-white to greenish-gray. The best green transparent specimens are from the Mussa Alp and Zillerthal, but it is also found in the Urals and the United States.

FLUOR SPAR.

This mineral occurs in many colors, often approaching the finer gems in appearance, and bearing the commercial names of false ruby, false emerald, false topaz, etc., etc., according to its color.

Fluor spar is brittle, 4 in hardness, has the specific gravity of 3.1 to 3.2, single refraction, is transparent to translucent, has a vitreous lustre, phosphoresces when heated, is attacked by acids, and melts before the blow-pipe. It is composed of:

Fluorine 48.7
Calcium 51.3

White, yellow, green, rose- and crimson-red, violet-blue, sky-blue, and brown, wine-yellow, greenish-blue, and gray are the colors of this many-tinted mineral.

Fluor spar is found in England, Norway, Baden, Nova Scotia, Thuringia, the Alps, Saxony, and the United States.

Large pieces of this mineral are made into beautiful vases and ornaments.

HYPERSTHENE.

Handsome specimens of hypersthene or Labrador hornblende are used for ornamental purposes.

This mineral is found in crystalline masses, has the hardness of 6, specific gravity 3.3 to 3.4, lustre pearly to metallic. It is translucent to opaque, brittle, and fuses before the blow-pipe. It consists of:

Silica 54.2
Magnesia 24.1
Protoxide of iron 21.7

Hypersthene occurs in dark-brown, green, grayish-black, greenish-black, and jet-black colors, and is found in the isle of Skye, the Hartz Mountains, Saxony, Labrador, Greenland, Norway, Sweden, Bohemia, Thuringia, and the United States.

QUARTZ.

The quartz group is the largest and most diversified among precious stones. Quartz occurs _massive_, in concretions, and in confused crystalline masses.

On account of the abundance of the massive kinds, such as jasper, agates, onyx, etc., some writers place the quartz group under the head of semi-precious stones, and lately the United States customs authorities have gone further in that direction, and have ruled that “because of the abundance and comparative cheapness of agates, onyxes, etc., they were no longer precious stones.” This position, however, the custom-house speedily abandoned, and, for dutiable purposes at least, the quartz family, in all its ramifications, is recognized as belonging to the precious stones.

Harder than the tourmaline, turquois, or opal, as hard as the chrysolite, and nearly as hard as the garnet or emerald, there is no reason why the crystallized varieties, such as amethyst, cairngorm, false topaz, chrysoprase, and even the cat’s-eye and finer onyxes, should not be classed among the precious stones.

Some more plentiful and less beautiful varieties of quartz are not valuable, and they take the same position in the quartz family that the huge imperfect crystals do in the beryl group. Whenever the specimen is sufficiently beautiful to be cut and polished for setting in jewelry, it should be included under the precious stones.

Quartz crystallizes in the rhombohedral system, and many varieties are found massive and compact. The cleavage is indistinct but can sometimes be found by plunging a heated crystal into cold water. The hardness of quartz is 7; specific gravity 2.5 to 2.8, the purest kinds being 2.65; the lustre is vitreous to resinous, and fracture conchoidal.

Quartz is tough, brittle, and feels cold; it becomes positively electric by rubbing, shows phosphorescence in the dark, and gives sparks if struck with another piece of quartz or with steel.

Quartz is transparent to translucent, semi-translucent to opaque, doubly refractive, and does not melt before the ordinary blow-pipe, but may be melted with the oxyhydrogen blow-pipe. It also melts with soda to a clear glass, and is soluble in fluohydric acid.

Quartz is composed of pure silica

Oxygen 53
Silicon 47

Some of the impure varieties contain oxide of iron, carbonate of lime, clay, and other minerals.

CRYSTALLIZED QUARTZ.

Colorless quartz or pure rock-crystal is found in many parts of the world, notably in Switzerland, Dauphiny, Piedmont, the Carrara quarries in Italy, Canada; in Herkimer County, New York, and on the shores of Lake George, in the same place; at Hot Springs, Arkansas; and along the beach of Long Branch, Cape May, and many other places.

Rock-crystal, commercially known as Bohemian diamond, occidental diamond, Lake George diamond, rhinestone, pebble, etc., etc., is colorless and transparent. This stone is largely used for optical purposes, and is also sometimes cut into brilliants to imitate the diamond.

While rock-crystal is considerably harder than strass or paste, it lacks, however, the brilliancy of the fine-composition imitation diamond.

Besides being much softer, the paste is often heavier than the crystal, because of the quantity of lead and other minerals used in its composition.

AMETHYST.

Amethystine quartz or amethyst varies in color from light to clear-dark purple, sometimes nearly black, and from light to dark bluish-violet. The coloring of the stone is supposed to be due to manganese.

The best amethysts come from Brazil and Ceylon, but good specimens are found in India, Persia, Botany Bay, Transylvania, near Cork and the island of May in Ireland, at Oberstein, in Saxony, in Hungary, Siberia, Nova Scotia, Sweden, Bohemia, Canada, and in the States of Maine, Pennsylvania, Colorado, Georgia, Virginia, and Michigan.

Under heat, the amethyst turns first yellow, then green, and finally becomes colorless. The value of an amethyst depends upon the fashion, and the time has been when these stones ranked among the most valuable of precious stones. At present, a fine amethyst can be bought for very little money, but should the stone become fashionable again, the best specimens will command good prices.

YELLOW QUARTZ.

Yellow quartz, known as false topaz, Bohemian, occidental, Indian, or Spanish topaz, resembles the real topaz in color, but is softer, lighter, different in crystallization and cleavage, and in electrical properties.

In color, this stone varies from the lightest yellow to orange-red and brown.

Most of the yellow quartz comes from Brazil, and much of it is changed to yellow by burning amethyst and smoky quartz.

CAIRNGORM, ETC.

Smoky yellow to smoky brown, often gray and black, are the tints of the cairngorm. This species of transparent quartz takes its name from Cairngorm in Invernessshire, in Scotland, a locality where some of the best specimens have been found. Pike’s Peak, Arkansas, and certain districts in North Carolina have also produced some very fine smoky topazes.

The cairngorm is used for seals, beads, and some of the cheaper jewels, and is largely sold at watering-places in Switzerland, and in the Western United States.

The stone is very popular in Scotland. Hair or needle stones is the name given to these varieties of crystallized quartz when they contain foreign substances, such as rutile, manganese, chlorite, etc., in hair or needle formation.

These stones are cut to represent the needle enclosures in an upright position, and are called sagenite or Venus hair stones or love arrows.

Iridescent or rainbow quartz is the variety of rock-crystal containing cracks and fissures which reflect all the colors of the rainbow. Quartz can also be artificially colored by rapidly cooling a heated specimen and then dipping the piece into a coloring preparation; the minute cracks in the quartz absorb the coloring matter, and the result is a red-, blue-, or green-tinted stone.

The massive varieties of quartz embrace the rose quartz, avanturine, cat’s-eye, crocidolite, heliotrope, chrysoprase, prase, plasma, chalcedony, agates, onyx, carnelian, jasper, hornstone, and flint.

ROSE QUARTZ.

Rose quartz occurs in a massive form, usually very imperfect and cracked, and varying in color from rose-red to pink. The color is supposed to be due to titanic acid, and often becomes paler on exposure.

This stone is nearly opaque and semi-transparent on the edges, has a greasy lustre, and specific gravity of 2.65 to 2.75. Rabenstein near Zwiesel in Bavaria, the United States, Brazil, France, Ceylon, Finland, and Siberia are places where rose quartz has been found.

AVANTURINE.

Avanturine is an opaque, yellow, brown, or red quartz, spangled with minute scales of mica or some other mineral, and found principally near Madrid, in Spain. It is also found in France, Scotland, Bavaria, the Urals, and Styria.

A beautiful imitation of avanturine, called goldstone, is manufactured of glass into which metal filings are introduced. This goldstone is superior to avanturine in every point except that of hardness. Avanturine and its imitation, but largely the latter, are used for the cheaper kinds of jewelry, and were very popular in the United States some years ago.

CAT’S-EYE.

The Hungarian, occidental, or quartz cat’s-eye is found on the coast of Malabar, Ceylon, Hartz Mountains, and Bavaria.

This stone is translucent to opaque, gray, green, brown, red, and the shadings of these colors, but usually a greenish-gray, with a mass of fine white lines in the centre, which give to the stone a chatoyant appearance.

The cat’s-eye is usually cut cabochon or carbuncle-shaped, and the lines (which are due to the fibres of asbestos) are kept in the centre of the stone, and play like the eye of a cat when the stone is moved.

The quartz cat’s-eye is easily distinguished from the oriental of chrysoberyl cat’s-eye, as it is softer and much lighter.

CROCIDOLITE.

Crocidolite or tiger-eye is a light-brown, brownish-yellow to dark-green, and greenish-blue quartz, which has the same chatoyant qualities as the cat’s-eye. When cut cabochon, the crocidolite is called tiger-eye.

This beautiful mineral was very rare some years ago, and good specimens were sold by the carat.

Great quantities, however, have lately been found in South Africa, and although the finest pieces are still used for cameos and intaglios, many objects, such as paperweights, umbrella handles, match-safes, etc., are now cut from this stone.

Crocidolite is often artificially colored to very closely imitate some of the finest shades of the oriental cat’s-eye.

HELIOTROPE.

Heliotrope or blood-stone, as this variety is commonly called, is a dark-green quartz, translucent to opaque, and covered with small red spots or blood-colored blotches, from which the stone derives the name of blood-stone.

This stone has long been used for seal and signet purposes, and many fine intaglios and cameos carved in blood-stone are in existence.

Bucharia, Tartary, Siberia, East India, China, the island of Rum in the Hebrides, the United States, and Canada are some of the places where the heliotrope is found.

CHRYSOPRASE.

The chrysoprase is an apple-green chalcedony, sometimes olive- or whitish-green. It is translucent, scratches glass, and has the specific gravity of 2.56.

The color is due to the presence of oxide of nickel. This stone is found principally in Silesia, but also in Siberia and the United States.

Large pieces of chrysoprase are rare, and even the best specimens lose their color in course of time.

PRASE.

A translucent, spotted leek-green, green quartz, which loses its polish on exposure to the air, is known as prase.

This stone is found principally in the iron mines of Brietenbaum, Saxony, and also in Brittany, the Tyrol, Scotland, Salzburg, Finland, and the United States.

Prase is sometimes known commercially as “mother of emerald,” and a greenish crystalline quartz is also often called prase.

PLASMA.

Plasma is a dark grass-green quartz, feebly translucent, and is sometimes covered with white or yellow spots. Plasma is somewhat lighter in weight than the heliotrope and does not take as fine a polish.

This stone is found in India, China, and in the Black Forest, Germany.

CHALCEDONY.

Chalcedony is cloudy or translucent, white, yellowish-gray, blackish-brown, light to dark-blue, milky-white, and black.

This quartz is sometimes nearly transparent, waxy in lustre, and in some varieties has a light gray and transparent base with dark cloudy spots. This last variety is called “cloudy chalcedony”. Another kind, with gray and white stripes alternating, is known as chalcedonyx.

Iceland, the Faroe Islands, Hüttenberg, Loben, Saxony, Hungary, Nubia, Nova Scotia, Oberstein, Ceylon, India, Siberia, Carinthia, the Hebrides, the United States, and Canada are places where chalcedony is found.

AGATES.

Agate is an improved variety of chalcedony and comprises the following kinds.

Banded or ribbon agate, running in delicate parallel layers.

Eye agate, forming concentric rings with a dark centre, giving the appearance of a human eye.

Fortification agate, running in circular parallel zigzag lines like the walls of a fortress.

Rainbow agate is a thin or concentric structure which when cut across and held towards the light shows an iridescence.

Moss agate, light-gray to white and translucent to opaque agates, display black tracings like fine moss or trees. Mocha or tree agates are covered with black, brown, or red figures, as of trees and plants.

Beckite or silicified coral shells, silicified wood, wood agate, wood opal, cloudy agate, and agate jasper are some of the many varieties of this class.

The common carnelians, blood-stones, and onyxes are usually counted among the agates.

Uruguay, Brazil, Oberstein, Silesia, Surinam, India, Arabia, Saxony, Scotland, the United States, and Canada are the principal places where agates are found.

ONYX OR AGATE ONYX.

Onyx is a variety of chalcedony in bands or strata of white, gray, and black, translucent to opaque, and generally found where agates abound.

The layers or bands are in even planes, and the colors, white and black, white and brown, or brown, white, and black, alternate. This stone is largely used for cameos, the base being usually of black or brown, and the engraved or upper part white- or cream-colored.

When one or more layers are of carnelian or sard, the stone is called sard-onyx. Sard is a rich brown color inclining to red, and when held against the light shows a red hue.

Onyx and sard-onyx are often artificially improved by boiling the stones in honey, oil, or sugar water, and then in sulphuric acid. The acid carbonizes the sugar or oil which the stone has absorbed and gives it a deeper color.

For red, protosulphate of iron is added, and for a blue color to imitate lapis lazuli, yellow prussiate of potash is added to the protosulphate of iron.

Only the porous parts of the stones, usually the dark parts, absorb the sugar or oil, and so aid the contrast of the colored with the white layers.

CARNELIAN.

Carnelian is a clear red translucent chalcedony, and is usually of a gray or grayish-red color. Several weeks of exposure to the sun’s rays and subsequent heating in earthen pots enhances and deepens the color.

The brownish-red or dark-brown carnelian is called sardoine or sard; the blood-red to pink varieties, with an upper layer of white onyx, are called carnelian onyx, and the stones with a brown or sard base and a white top are called sard-onyx.

Carnelians are sometimes of a yellowish-brown or yellow color, but red to brown are the principal colors.

The secret of coloring agates was discovered in the early part of this century, and about the same time agates became scarce in Oberstein, while large finds were made in Brazil and Uruguay, especially of agates with red layers. This variety comes chiefly from Brazil.

Besides Uruguay and Brazil, carnelian is found in Arabia and India. The most beautiful specimens of intaglios are engraved on sardoine, and some of the finest cameos extant are of sard and carnelian onyx.

JASPER.

Jasper is an impure opaque quartz, usually containing more iron than agate, and lacking the quality of translucency. Jasper occurs in red, brown, ochre-yellow, dark green, brownish-green, grayish-black, and grayish-blue; sometimes containing bands or spots or quartz formations, and often found with regular zones or bands of various colors.

Egyptian jasper or Egyptian pebbles are names given to varieties that are usually brown with inner bands of lighter hue, approaching cream in color, and sometimes having dark bands with spots or markings.

Egyptian jasper is found near Grand Cairo, and other varieties are found in the Urals, Saxony, Devonshire, Nova Scotia, Canada, and the United States.

The specific gravity of jasper varies from 2.31 to 2.67; it scratches glass, but yields to rock-crystal.

FALSE LAPIS.

False lapis is jasper or agate artificially colored blue to imitate the true lapis. Lapis lazuli is softer than false lapis, being only 5 to 5.5 in hardness.

Sappharine or siderite is a sapphire or sky-blue chalcedony occurring in Salzburg.

Nicolo is a variety of onyx with a black or brown base and a band or layer of bluish-white on top. The upper layer is not flat, but convex, and is always thicker than the lower one.

HEMATITE.

Hematite was once largely used to engrave upon, many of the ancient intaglios being on this mineral. It is now cut to simulate black pearls, and is also used in the cheaper jewelry, both engraved and cut cabochon.

Hematite has the hardness of 5.5 to 6.5, and specific gravity, 4.2 to 5.3; it is opaque, and shows a red streak when scratched. It is composed of:

Iron 70
Oxygen 30

The colors of hematite are dark-steel gray to iron-black, and sometimes brownish- to blood-red. The lustre is highly metallic, with slight iridescence.

The island of Elba, France, Switzerland, Italy, Norway, Sweden, Bohemia, England, Brazil, Chili, Canada, Spain, and the United States are places where hematite is found. The Germans call this mineral “blood-stone,” and it is also known as specular iron ore and iron glance.

OBSIDIAN.

Obsidian, or volcanic glass, does not occupy a high position as a gem or as an ornamental stone, but its antiquity and occasional use among the agates and semi-precious stones will justify its mention.

This mineral is a melted lava, and consists of silex, alumina, and a little potassa, soda, and oxide of iron. Obsidian is 6 to 7 in hardness, has a specific gravity of 2.25 to 2.8, is sometimes transparent but mostly translucent to opaque, and is vitreous to metallic in lustre. It is brittle and not easily attacked by acids. It melts before the blow-pipe and takes a high polish.

Obsidian comes from volcanoes, and is found in Iceland, Teneriffe, Lepare islands, Peru, Mexico, Sicily, and on all volcanoes. The color is velvety-black to gray, brown, greenish-black, yellow, blue, bottle-green, and white, seldom red, and often with black or yellow spots or veinings.

Iceland agate lava, volcanic lava, and royal agate are all obsidian.

MALACHITE.

Malachite although sometimes used for jewelry, is now more largely employed for mosaic work and ornamental vases, and is sufficiently costly and rare to be classed amongst the precious stones.

Malachite is 3.5 to 4 in hardness; has a specific gravity of 3.6 to 4; is translucent to opaque; the lustre is vitreous to adamantine. It is attacked by acids, and melts before the blow-pipe. It is composed of:

Carbonic acid 20.
Protoxide of copper 71.8
Water 8.

Malachite occurs in emerald or verdigris green color, sometimes in alternating stripes of different shades of green, and occasionally in leek- to blackish-green.

Malachite is found in Russia, France, the Tyrol, England, Scotland, Ireland, Germany, Africa, Chili, Australia, and the United States.

The finest specimens are found in the Urals—a block three and a half feet square, being valued at 525,000 roubles.

JET.

The making of jet or mourning jewelry was once a very large industry in France and England, and even now Whitby jet is well known in commerce.

Jet is a species of bituminous coal (cannel coal) which can be cut with a knife. The hardness is 1 to 2.5; specific gravity, 1.35; its lustre is not very high, and color pitch-black.

It is found in England, France, Hesse, Spain, Italy, and Prussia.

AMBER.

Amber is a fossil, and is not to be classed amongst minerals, but this material has always been used as an ornament, and a few notes will not be out of place here.

This vegetable fossil, which has been known to the world for ages, the Greeks called electron.

It is very light, having a specific gravity of 1.065 to 1.08, and is 2 to 2.5 in hardness.

The principal color is yellow, in various shades, sometimes running into white or reddish-brown and black.

Amber is transparent to translucent, possesses single refraction, a resinous lustre to a high degree, becomes electric by rubbing, and burns readily before the blow-pipe.

Amber when heated becomes soft and pliable.

Amber is composed of:

Carbon 79.
Hydrogen 10.5
Oxygen 10.5

Amber is imitated by gum copal, and even the insect enclosures which occur in real amber are copied.

These imitations can be detected by placing the specimen in water or alcohol. This is also a good test for pieces of real amber that have been melted or glued together.

Amber is thrown up by the sea, in rivers near the sea, or on the sea-shore, and has been found in nearly all parts of the world.

The Russian, Baltic, and Sicilian coasts have yielded the larger portion of the production, but supplies come also from Galizia, the Urals, Poland, China, and the United States.

For ornamental purposes the faceted amber beads are largely used, but of late years these have been closely imitated in glass.

CORAL.

Coral, although not a precious stone, has been largely used in jewelry, and as some of this beautiful substance is very valuable, a few words will not come amiss.

Red or precious coral is the work of a family of zoöphytes which live mostly in cavities of rock in the sea.

These polyps build their homes at a depth of two to seven hundred feet under the surface of the sea, and although the single groups of coral are sometimes several feet long, the usual size is about twelve inches high, and about one inch at the thickest part of any single branch.

Coral is usually red, and rarely white or black, while the pale rose-pink is the most esteemed color.

Coral is mostly found at Calle, off the coast of Africa, but also on the coasts of Tunis, Algiers, Corsica, Barbary, Majorca, and Minorca.

Coral fishing-vessels leave Italy the beginning of March and return from the African coast in October; at one time as many as four hundred vessels were engaged in this industry.

TABLE OF HARDNESS AND SPECIFIC GRAVITY.

────────────────────┬───────────┬──────────────
│ HARDNESS. │ SPECIFIC
│ │ GRAVITY.
────────────────────┼───────────┼──────────────
Achroite │ 7. — 7.5 │ 3. — 3.1
Alexandrite │ 8.5 │ 3.65 — 3.8
Almandine │ 7.5 │ 4. — 4.2
Almandite │ 7.5 │ 4. — 4.2
Amber │ 2. — 2.5 │ 1.065 — 1.08
Apatite │ 4.5 — 5. │ 2.95 — 3.25
Axinite │ 6.5 — 7. │ 3. — 3.3
Beryl │ 7.5 — 8. │ 2.67 — 2.73
Bobrowska garnet │ 6. │ 3.85
Bohemian " │ 7.5 │ 3.69 — 3.78
Brazilian emerald │ 7. — 7.5 │ 3. — 3.1
" sapphire │ 7. — 7.5 │ 3. — 3.1
Cachelong │ 5.5 — 6. │ 2. — 2.1
Cat’s-eye │ 8.5 │ 3. — 3.8
Ceylon chrysolite │ 7. — 7.5 │ 3. — 3.1
" peridot │ 7. — 7.5 │ 3. — 3.1
Chrysoberyl │ 8.5 │ 3.65 — 3.8
Chrysolite │ 6.5 — 7. │ 3.3 — 3.5
Chrysoprase │ 7. │ 2.56
Cinnamon stone │ 6.5 │ 3.5 — 3.56
Cyanite │ 5. — 7. │ 3.45 — 3.7
Cymophane │ 8.5 │ 3.65 — 3.8
Demantoide │ 6. │ 3.85
Diamond │10. │ 3.5 — 3.6
Dichroite │ 7. — 7.5 │ 2.56 — 2.67
Diopside │ 5. — 6. │ 2.9 — 3.5
Emerald │ 7.5 — 8. │ 2.67 — 2.73
Epidote │ 6. — 7. │ 3.32 — 3.50
Essonite │ 6.5 │ 3.5 — 3.56
Euclase │ 7.5 │ 3.1
Fluor spar │ 4. │ 3.1 — 3.2
Garnet │ 5. — 8. │ 3.15 — 4.3
Grossularite │ 6.5 │ 3.5 — 3.56
Hematite │ 5.6 — 6.5 │ 4.2 — 5.3
Hiddenite │ 6.5 — 7. │ 3.13 — 3.19
Hyacinth │ 7.5 │ 4.4 — 4.7
Hydrophane │ 5.5 — 6. │ 2. — 2.1
Hypersthene │ 6. │ 3.3 — 3.4
Idocrase │ 6.5 │ 3.35 — 3.45
Indicolite │ 7. — 7.5 │ 3. — 3.1
Jacinth │ 7.5 │ 4.4 — 4.7
Jargoon │ 7.5 │ 4.4 — 4.7
Jasper │ 7. │ 2.31 — 2.67
Jet │ 2.5 │ 1.35
Labrador │ 6. │ 2.62 — 2.76
" hornblende │ 6. │ 3.3 — 3.4
Lapis lazuli │ 5. — 5.5 │ 2.38 — 2.42
Malachite │ 3.5 — 4. │ 3.6 — 4.
Moonstone │ 6. — 6.5 │ 2.4 — 2.6
Obsidian │ 6. — 7. │ 2.25 — 2.8
Olivine │ 6.5 — 7. │ 3.3 — 3.5
Opal │ 5.5 — 6. │ 2. — 2.1
Oriental amethyst │ 9. │ 3.9 — 4.1
" aquamarine │ 9. │ 3.9 — 4.1
" chrysolite │ 9. │ 3.9 — 4.1
" emerald │ 9. │ 3.9 — 4.1
" hyacinth │ 9. │ 3.9 — 4.1
" topaz │ 9. │ 3.9 — 4.1
Pearl │ │ 2.5 — 2.7
Peridot │ 6.5 — 7. │ 3.3 — 3.5
Phenacite │ 7.5 — 8. │ 2.96 — 3.
Pyrope │ 7.5 │ 3.69 — 3.78
Quartz │ 7. │ 2.5 — 2.8
" cat’s-eye │ 6. — 6.5 │ 2.65
Rose quartz │ 7. │ 2.65 — 2.75
Rubellite │ 7. — 7.5 │ 3. — 3.1
Ruby │ 9. │ 3.9 — 4.1
" cat’s-eye │ 9. │ 3.9 — 4.1
Sapphire │ 9. │ 3.9 — 4.1
" cat’s-eye │ 9. │ 3.9 — 4.1
Siberite │ 7. — 7.5 │ 3. — 3.1
Sphene │ 5. — 5.5 │ 3.4 — 3.56
Spinel │ 8. │ 3.5 — 3.6
Spodumene │ 6.5 — 7. │ 3.13 — 3.19
Star ruby │ 9. │ 3.9 — 4.1
" sapphire │ 9. │ 3.9 — 4.1
" topaz │ 9. │ 3.9 — 4.1
Sunstone │ 6. — 7. │ 2.56 — 2.72
Syrian garnet │ 7.5 │ 4. — 4.42
Titanite │ 5. — 5.5 │ 3.4 — 3.56
Topaz │ 8. │ 3.4 — 3.6
Tourmaline │ 7. — 7.5 │ 3. — 3.1
Turquois │ 6. │ 2.6 — 2.8
Uwarowite │ 7.5 │ 3.41 — 3.52
Vesuvianite │ 6.5 │ 3.35 — 3.45
Water sapphire │ 7. — 7.5 │ 2.56 — 2.67
────────────────────┴───────────┴──────────────

GENERAL INDEX.

Achroite, 64
Actinolite, 29
Adularia, see moonstone
Agate jasper, 120
Agate onyx, see onyx
Agate, see quartz, 106, 119, 122, 123, 124, 126
Alexandrite, 8, 54, 56
Almandine, 9, 30, 80
Almandite, 29, 80
Amazon stone, 17, 88, 91
Amber, 17, 128
American ruby, 80, 83
Amethyst, 8, 9, 16, 17, 44, 49, 107, 110, 111
Amethystine quartz, see amethyst
Antimony, 29
Apatite, 19, 87
Aquamarine, 8, 16, 53
Aquamarine chrysolite, 53
Arizona ruby, 80, 83
Asterias, see star sapphires
Aurora red sapphire, see Oriental hyacinth
Avanturine, 113, 114
Avanturine felspar, see sunstone
Axinite, 17, 102