Geol 1403 LAB First
exam Minerals with
100% CORRECT
ANSWERS
Albite
(Plagioclase Feldspar) NaAlSi3O6 (Sodium aluminum silicate)
Crystal habit: tabular, granular, blocky, massive, Cleavage: 2 directions @ 90°,
Fracture: uneven opposite cleavages, Striations: common on cleavage planes,
Tenacity: brittle, Hardness: 6, white to pale gray, Streak: white to none, Luster:
vitreous, Specific gravity: 2.6-2.8 (medium), Diaphaneity: opaque, Use:
“Moonstone” gem if opalescent.
Apatite
Ca5(PO4)3(F,Cl,OH) (Calcium-fluoro-chloro-hydroxyl phosphate)
Crystal form: Hexagonal, Crystal habit: prismatic, Cleavage: poor (not visible),
Fracture: conchoidal to uneven, Striations: visible on crystal faces (if present),
Tenacity: brittle, Hardness: exactly 5 on Mohs' scale, Color: green to brown,
Streak: white, Luster: vitreous, Specific gravity: 3.1-3.2 (high), Diaphaneity:
transparent to opaque, Use: fertilizer (phosphate) and gemstones
Augite
(Ca,Na)(Mg,Fe,Al)(Si,Al)2O6
Crystal habit: irregular masses, Cleavage: 2 directions @ 87° & 93°, Fracture:
uneven opposite cleavages, Tenacity: brittle, Hardness: 5-6, Color: dark green to
, black, Streak: none, Luster: vitreous to dull, Specific gravity: 3.0-3.5 (high),
Diaphaneity: opaque, Use: interest to collectors.
Biotite
K(Mg,Fe)3(AlSi3O10)(OH)2 (Hydrous Potassium, magnesium iron, aluminum
silicate)
Crystal habit: micaceous (sheet-like), Cleavage: perfect (basal) 1 direction,
Fracture: uneven opposite cleavage, Tenacity: elastic, Hardness: 2.5-3, Color: dark
brown-black, Streak: white to gray (if pieces are thick enough for testing), Luster:
vitreous to pearly, Specific gravity: 2.8-3.1 (medium), Diaphaneity: translucent
(thin sheets) to opaque, feel: similar to plastic, Use: interest to collectors, Other:
mineral separates into thin sheets along cleavage planes.
Calcite
CaCO3 (Calcium carbonate)
Crystal form: scalenohedral (if present), hexagonal (if present), Crystal habit:
rhombohedra, scalenohedral, tabular, or prisms, Cleavage: perfect rhombohedral,
3 directions not @ 90°, Fracture: not recognizable, Tenacity: brittle, Hardness:
exactly 3 on Mohs' scale, Color: varies widely, Streak: white to gray, Luster:
vitreous to dull, Specific gravity: 2.71 (medium), Diaphaneity: translucent to
opaque, double refraction: visible through colorless rhombs, reaction to HCl acid:
effervesces (bubbles) vigorously, Use: fertilizer (lime), Portland cement, building
stones such as limestone and marble.
corundum
Al2O3 (Aluminum oxide) Crystal form: hexagonal, Crystal habit: barrel shaped,
tabular or massive (emery), Fracture: conchoidal, Striations: may be visible on
basal surfaces, Tenacity: brittle, Hardness: exactly 9 on Mohs' scale, Color: brown,
blue, pink, red, etc., Streak: none, Luster: vitreous to dull, Specific gravity: 4
exam Minerals with
100% CORRECT
ANSWERS
Albite
(Plagioclase Feldspar) NaAlSi3O6 (Sodium aluminum silicate)
Crystal habit: tabular, granular, blocky, massive, Cleavage: 2 directions @ 90°,
Fracture: uneven opposite cleavages, Striations: common on cleavage planes,
Tenacity: brittle, Hardness: 6, white to pale gray, Streak: white to none, Luster:
vitreous, Specific gravity: 2.6-2.8 (medium), Diaphaneity: opaque, Use:
“Moonstone” gem if opalescent.
Apatite
Ca5(PO4)3(F,Cl,OH) (Calcium-fluoro-chloro-hydroxyl phosphate)
Crystal form: Hexagonal, Crystal habit: prismatic, Cleavage: poor (not visible),
Fracture: conchoidal to uneven, Striations: visible on crystal faces (if present),
Tenacity: brittle, Hardness: exactly 5 on Mohs' scale, Color: green to brown,
Streak: white, Luster: vitreous, Specific gravity: 3.1-3.2 (high), Diaphaneity:
transparent to opaque, Use: fertilizer (phosphate) and gemstones
Augite
(Ca,Na)(Mg,Fe,Al)(Si,Al)2O6
Crystal habit: irregular masses, Cleavage: 2 directions @ 87° & 93°, Fracture:
uneven opposite cleavages, Tenacity: brittle, Hardness: 5-6, Color: dark green to
, black, Streak: none, Luster: vitreous to dull, Specific gravity: 3.0-3.5 (high),
Diaphaneity: opaque, Use: interest to collectors.
Biotite
K(Mg,Fe)3(AlSi3O10)(OH)2 (Hydrous Potassium, magnesium iron, aluminum
silicate)
Crystal habit: micaceous (sheet-like), Cleavage: perfect (basal) 1 direction,
Fracture: uneven opposite cleavage, Tenacity: elastic, Hardness: 2.5-3, Color: dark
brown-black, Streak: white to gray (if pieces are thick enough for testing), Luster:
vitreous to pearly, Specific gravity: 2.8-3.1 (medium), Diaphaneity: translucent
(thin sheets) to opaque, feel: similar to plastic, Use: interest to collectors, Other:
mineral separates into thin sheets along cleavage planes.
Calcite
CaCO3 (Calcium carbonate)
Crystal form: scalenohedral (if present), hexagonal (if present), Crystal habit:
rhombohedra, scalenohedral, tabular, or prisms, Cleavage: perfect rhombohedral,
3 directions not @ 90°, Fracture: not recognizable, Tenacity: brittle, Hardness:
exactly 3 on Mohs' scale, Color: varies widely, Streak: white to gray, Luster:
vitreous to dull, Specific gravity: 2.71 (medium), Diaphaneity: translucent to
opaque, double refraction: visible through colorless rhombs, reaction to HCl acid:
effervesces (bubbles) vigorously, Use: fertilizer (lime), Portland cement, building
stones such as limestone and marble.
corundum
Al2O3 (Aluminum oxide) Crystal form: hexagonal, Crystal habit: barrel shaped,
tabular or massive (emery), Fracture: conchoidal, Striations: may be visible on
basal surfaces, Tenacity: brittle, Hardness: exactly 9 on Mohs' scale, Color: brown,
blue, pink, red, etc., Streak: none, Luster: vitreous to dull, Specific gravity: 4
