Laboratory Manual for Introductory Geology 4e

APPENDIX 3.2
Determinative Tables for Systematic Mineral Identification
TABLE 2 Minerals with nonmetallic luster (continued)
Streak
Cleavage or
fracture
H Color Other diagnostic properties Mineral name
(composition)
Blue
Reddish
brown
— 3.5 Intense blue Often in platy crystals or spherical
masses; reacts with HCl; SpG = 3.77
— — Reddish brown Usually in earthy masses; also
occurs as black, metallic crystals;
SpG = 5.5–6.5
— — Brown, tan Earthy, powdery masses and
coatings on other minerals;
SpG = 3.6–4
Azurite
Cu 3
(CO 3
) 2
(OH) 2
Hematite
Fe 2
O 3
Limonite
FeO(OH) ⋅ nH 2
O
Yellowbrown
Three directions
not at 90°
3.5–4 Light to dark
brown
Often in rhombic crystals; reacts
with hot HCl; SpG = 3.96
Siderite
FeCO 3
Six directions, few
of which are usually
visible
3.5 Brown, white,
yellow, black,
colorless
Resinous luster;
SpG = 3.9–4.1
Sphalerite
ZnS
Three directions
at 90°
2.5 Colorless, white Cubic crystals or massive
(rock salt); salty taste; SpG = 2.5
Halite
NaCl
Three directions
not at 90°
3 Varied; usually
white or colorless
Rhombic or elongated crystals;
reacts with HCl; SpG = 2.71
Calcite
CaCO 3
White
or
colorless
Three directions
not at 90°
Three directions
at 90°
3.5–4 Varied; commonly
white or pink
Rhombic crystals; powder reacts
with HCl but crystals may not;
SpG = 2.85
3–3.5 Colorless, white SpG = 4.5 (unusually high for a
nonmetallic mineral)
Dolomite
CaMg(CO 3
) 2
Barite
BaSO 4
Four directions 4 Colorless, purple,
yellow, blue, green
One direction, poor 5 Usually green or
brown
Often in cubic crystals;
SpG = 3.18
Elongate 6-sided crystals; may be
purple, blue, colorless;
SpG = 3.15–3.20
Fluorite
CaF 2
Apatite
Ca 5
(PO 4
) 3
(OH,Cl,F)
(c) Hardness between 5.5 and 9 (harder than glass or a knife; softer than a streak plate)
Streak
Cleavage or
fracture
H Color Other diagnostic properties Mineral name
(composition)
Conchoidal fracture 7 Red, green, brown,
black, colorless,
pink, orange
Two directions at 90° 6 Colorless, salmon,
gray, green, white
Equant 12-sided crystals;
SpG = 3.5–4.3
Stubby prismatic crystals;
three polymorphs: orthoclase,
microcline, sanidine; may show
exsolution lamellae;
SpG = 2.54–2.62
Garnet family
Complex Ca, Fe, Mg,
Al, Cr, Mn silicate
Potassium feldspar
KAlSi 3
O 8
80 CHAPTER 3 MINERALS