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)
Two directions at 90° 6 Colorless, white, gray,
black
Striations (fine lines) on one of
the two cleavage directions; solid
solution between Na (albite) and
Ca (anorthite) plagioclase; SpG =
2.62–2.76
Plagioclase feldspar
CaAl 2
Si 2
O 8
,
NaAlSi 3
O 8
White
or
colorless
Conchoidal fracture 7 Colorless, pink,
purple, gray, black,
green, yellow
Elongate 6-sided crystals;
SpG = 2.65
Rarely seen 7.5 Gray, white, brown Elongate 4-sided crystals;
SpG = 3.16–3.23
One direction 6–7 White, rarely green Long, slender crystals, often
fibrous; SpG = 3.23
Quartz
SiO 2
Andalusite
Al 2
SiO 5
Sillimanite
Al 2
SiO 5
One direction 5 and 7 Blue, blue-gray to
white
Conchoidal fracture 6.5–7 Most commonly
green
Bladed crystals; two hardnesses:
H = 5 parallel to long direction
of crystal, H = 7 across the long
direction
Stubby crystals and granular
masses; solid solution between Fe
(fayalite) and Mg (forsterite)
Kyanite
Al 2
SiO 5
Olivine family
Fe 2
SiO 4
, Mg 2
SiO 4
Colorless
to
light
green
Two directions at
56° and 124°
Two directions at
56° and 124°
5–6 Dark green to black An amphibole with
elongate crystals;
SpG = 3–3.4
5–6 Pale to dark green An amphibole with
elongate crystals;
SpG = 3–3.3
Hornblende Complex
double-chain silicate
with Ca, Na, Fe, Mg
Actinolite
Double-chain silicate
with Ca, Fe, Mg
Two directions at
87° and 93°
5–6 Dark green to black A pyroxene with elongate crystals;
SpG = 3.2–3.3
Augite
Single-chain silicate
with Ca, Na, Mg, Fe, Al
One direction
perfect, one poor;
not at 90°
6–7 Apple green to black Elongate crystals and
fine-grained masses;
SpG = 3.25–3.45
Epidote
Complex twin silicate
with Ca, Al, Fe, Mg
No streak;
mineral
scratches
streak
plate
One direction,
imperfect
7.5–8 Blue-green, yellow,
pink, white; gem
variety: emerald
(green)
— 7–7.5 Dark brown, reddish
brown, brownish black
No cleavage 9 Gray, light brown; gem
varieties red (ruby),
blue (sapphire)
6-sided crystals with flat ends;
SpG = 2.65–2.8;
Stubby or cross-shaped crystals;
SpG = 3.65–3.75
6-sided crystals with flat ends
Beryl
Be 3
Al 2
Si 6
O 18
Staurolite
Hydrous Fe, Al silicate
Corundum
Al 2
O 3
APPENDIX 81