Final Chapters 1 and 2

Question 1

Is color a reliable way to identify minerals?

Answer 1

-No, color is not a reliable way to identify minerals
-slight impurities or defects within the crystal structure may change the color

Question 2

What can you see to tell quartz from feldspar?

Answer 2

Quartz: has zero cleavages and glitters, usually clear
Feldspar: has cleavages and flashes, usually cloudy

Question 3

What can you see to tell calcite from quartz?

Answer 3

-calcite has three cleavages (rhombic)
-quartz has no cleavages

Question 4

In the field you tend not to carry a glass plate, but many geologists do often carry a jackknife. How can you
tell fine-grained snowy white calcite from similar-looking gypsum or quartz using hardness?

Answer 4

-calcite (3) and gypsum (2) would both be scratched by the jackknife (5.5)
-quartz (7) will not be scratched by the jackknife (5.5)

Question 5

How many cleavages does feldspar have? At what angle do they intersect? How do you tell plagioclase from
K-spar?

Answer 5

-feldspar has two cleavages
-the angles intersect at 90˚
-you can tell plagioclase (striations) from k-spar (veinlets) from the veinlets and striations

Question 6

How do you tell amphibole from pyroxene?

Answer 6

amphibole: 2 cleavage planes that intersect at ~60° or 120°, the cleavages are highly reflective, tends to form elongate rectangular crystals

pyroxene: 2 cleavage planes that intersect at ~90°, cleavage planes tend to appear dull, crystals tend to be blocky

Question 7

what color streak does hematite have? magnetite? sphalerite?

Answer 7

Hematite: red to red-brown streak
Magnetite: black
Sphalerite: yellow

Question 8

How many cleavages does calcite have, and at what angle(s) do they intersect?

Answer 8

-three cleavages
-the cleavages don’t intersect at 90°, the shape will appear more rhombic

Question 9

How many cleavages does galena have, and at what angle(s) do they intersect?

Answer 9

-three cleavages
-the cleavages intersect at 90°

Question 10

How many cleavages do quartz and olivine have?

Answer 10

-both have zero cleavages

Question 11

What is the hardest mineral? And the softest?

Answer 11

Hardest: diamond
Softest: talc

Question 12

Which mineral did you see that has four cleavages? Six?

Answer 12

Four cleavages: fluorite
Six cleavages: sphalerite

Question 13

Which mineral has a pearly luster?

Answer 13

most notably talc; also, chlorite, gypsum

Question 14

Which mineral feels slippery/soapy/greasy?

Answer 14

talc, serpentine, graphite

Question 15

How can you tell if you have a sulfide mineral, like sphalerite?

Answer 15

faint odor of hydrogen sulfide (rotten eggs)

Question 16

Is it ore-forming minerals or rock-forming minerals that tend to have metallic lusters?

Answer 16

ore-forming minerals tend to have metallic lusters