Chapter I: Front Matter

BUREAU OF ECONOMIC GEOLOGY
The University of Texas at Austin
Austin, Texas 78712

JOHN T. LONSDALE, _Director_

Report of Investigations—No. 42

Texas Gemstones

By
Elbert A. King, Jr.

February 1961

_Second Printing—February 1963
Third Printing—September 1972
Fourth Printing—March 1983
Fifth Printing—August 1991_

Contents

Page
Introduction 5
Properties of gemstones 5
Crystals 7
Cutting and polishing of gemstones 10
Cabochon gems 10
Faceted gems 13
Tumbled gems 17
Texas gemstones 18
Amber 18
Augite 18
Beryl 18
Celestite 19
Diamond 19
Epidote 19
Fluorite 20
Fossil wood 20
Gadolinite 21
Garnet 22
Jet 22
Labradorite 23
Microcline 23
Obsidian 24
Opal 24
Pearl 24
Quartz 25
Crystalline varieties 25
Amethyst 25
Citrine 25
Rock crystal 26
Rose quartz 26
Smoky quartz 26
Cryptocrystalline varieties 27
Chalcedony 27
Agate 27
Agatized wood 27
Carnelian 27
Jasper 27
Sanidine 28
Spinel 28
Tektite (bediasite) 28
Topaz 29
Tourmaline 30
Turquoise 31
Glossary 32
Selected references 34
Index 41

Illustrations

Figures— Page
1. Typical crystal form of three common Texas gemstones 9
2. Variations of the cabochon cut 10
3. Diamond saw 11
4. Cabochon properly attached to dop-stick 12
5. Cabochons at various stages of cutting and polishing 12
6. Nomenclature of the standard American brilliant cut 13
7. Facet table 14
8. Grinding the table facet on a rough stone 15
9. Stone dopped to table facet 15
10. Preformed stone dopped to table facet 16
11. Proper sequence of cutting of the pavilion facets 16
12. Proper placing of pavilion girdle facets 17
13. Proper sequence of cutting of crown facets 17
14. Common crystal form of Travis County celestite 19
15. Common crystal form of fluorite 20
16. Crystal faces on microcline specimen shown in Plate III 23
17. Common crystal form of spinel 28
18. Crystal faces on topaz crystal shown in Plate V 29
19. Cross section through irregularly colored stone 30
20. Common crystal form of Llano County tourmaline 31

Plates— Page
I. A, Gem-quality celestite crystals from Travis County. B,
Opalized wood from the Texas Gulf Coastal Plain 35
II. A, Gem-quality garnet crystals and faceted gem from Gillespie
County. B, Labradorite from Brewster County 36
III. A, Pink microcline crystal. B, Smoky quartz. Both from Burnet
County 37
IV. Polished agate from gravels of the Rio Grande near Zapata,
Zapata County 38
V. A, Texas tektites (bediasites). B, Topaz crystal from a
pegmatite dike near Streeter, Mason County 39
VI. A, Topaz from stream gravels near Streeter, Mason County. B,
Tourmaline crystals in schist from Llano County 40

Table 1. Properties of some common Texas gem minerals 8

Texas Gemstones

ELBERT A. KING, JR.