Chapter I: Metallic Luster, Streak Colored

C—color H—hardness Remarks Name and
S—streak Cl—cleavage composition
F—fracture
A. Hardness not more than 2.5

C—lead gray H—2.5 Very heavy; occurs as Galena (31)
S—black Cl—cubic; crystals, grains, or PbS
perfect in 3 masses; easily
directions identified by color and
F—subconchoidal cleavage
or even
C—copper red H—2.5 Very heavy; apt to have Native copper
S—metallic, Cl—none green coating; distorted Cu
shiny F—jagged or wirelike forms;
malleable

B. Hardness greater than 2.5 but not greater than 6.5

C—yellow-brown H—5.5 (may be as In earthy masses; Limonite (29)
to black low as 1) coloring material in FeO(OH)·H₂O
S—yellow-brown Cl—none many sandstones,
F—uneven conglomerates, and
soils; often mixed with
and difficult to
distinguish from
goethite and other iron
minerals
C—brassy yellow H—6 As compact masses, Pyrite (28)
S—greenish black Cl—poor grains, cubes, and in 8- FeS₂
F—conchoidal to and 12-sided crystals;
uneven commonly associated with
coal, and with lead-zinc
ores of northwestern
Illinois
C—pale brassy H—6 As fibrous, radiating, Marcasite
yellow to Cl—poor tabular, and cocks-comb FeS₂ (28)
silver white F—uneven crystals or compact
S—greenish gray masses; usually lighter
colored than pyrite, but
difficult to distinguish
from pyrite; associated
with coal, and with
lead-zinc ores of
northwestern Illinois