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Geology 101 > Minerals > Flashcards

Flashcards in Minerals Deck (9)
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1

Quartz

Hardness = 7 scratches glass
Breaks by (conchoidal) fracture.
Vitreous (oily) luster

2

Quartz Crystal

Hardness = 7
Breaks by conchoidal fracture
Tetrahedral crystal

3

Plagioclase Feldspar

Hardness = 6 – scratches glass
Breaks along two planes of cleavage at about 90o
Striations appear on cleavage surface

4

K-Feldspar

Hardness = 6
Breaks along two planes of cleavage at about 90o
Exsolution lamellae (“muscle fibers”) run across the cleavage plane

5

Amphibole

Hardness = 6, scratches glass
Breaks along two cleavage planes greater than 90o (cleavage at 60o and 120o)
Splintery cleavages, black color

6

Calcite

Hardness = 3
Breaks along three planes of cleavage, rhombic shape shape
Reacts in HCl

7

Hematite

Hardness = 2.5
Breaks by fracture
Earthy luster
Leaves red-brown streak

8

Muscovite Mica

Hardness = 2, fingernail will scratch it
Breaks along one cleavage, planar or basal cleavage
Transparent in thin sheets

9

Biotite Mica

Hardness = 2, fingernail scratches it
Breaks along one cleavage or basal plane of cleavage
Black in color