Minerals

Question 1

Quartz

Answer 1

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

Question 2

Quartz Crystal

Answer 2

Hardness = 7
Breaks by conchoidal fracture
Tetrahedral crystal

Question 3

Plagioclase Feldspar

Answer 3

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

Question 4

K-Feldspar

Answer 4

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

Question 5

Amphibole

Answer 5

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

Question 6

Calcite

Answer 6

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

Question 7

Hematite

Answer 7

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

Question 8

Muscovite Mica

Answer 8

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

Question 9

Biotite Mica

Answer 9

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