sulfides 1-4 SET 1

Question 1

chalcocite formula

Answer 1

Cu2S

Question 2

chalcocite crystal form

Answer 2

• not in crystals
• commonly massive very fine grained
• if orthorhombic crystals, small and tabular with hexagonal outline, striated parallel to a axis

Question 3

chalcocite cleavage

Answer 3

conchoidal. poor prismatic 110

Question 4

chalcocite hardness

Answer 4

2.5 to 3, imperfectly sectile

Question 5

chalcocite specific gravity

Answer 5

5.5 to 5.8

Question 6

chalcocite color

Answer 6

• metallic, some soft and sooty
• shining leas gray, tarnished dull to black
• streak grayish black

Question 7

chalcocite occurrence

Answer 7

• one of the most important copper ore mineral
• most commonly as supergene mineral in enriched zone of sulfide deposits forming “chalcocite blanket” at water table
• primary mineral in hydrothermal veins (with bornite enargite chalcopyrite and pyrite)
• constituent of PCDs, disseminated throughout P granodiorite intrusives

Question 8

chalcocite remarks

Answer 8

lead gray color, low degree of hardness, slightly sectile

Question 9

bornite formula

Answer 9

Cu5FeS4

Question 10

bornite crystal form

Answer 10

• usually massive
• rarely tetragonal crystals

Question 11

bornite hardness

Answer 11

3

Question 12

bornite specific gravity

Answer 12

5.06 to 5.08

Question 13

bornite color

Answer 13

• metallic. streak grayish black
• brownish bronze on fresh
• tarnished to variegated purple and blue
• almost black on exposure

Question 14

bornite occurrence

Answer 14

• associated with chalcopyrite pyrite chacocite pyrrhotite covellite in hypogene deposits
• in supergene deposits less frequently in the upper enriched parts of copper veins
• disseminations in basic rocks
• contact metamorphic deposits
• pegmatites

Question 15

bornite remarks

Answer 15

fresh brown then tarnish to purple

Question 16

Galena formula

Answer 16

PbS

Question 17

Galena crystal form

Answer 17

• isometric, most common: cube, sometimes truncated by octahedron
• commonly coarse to fine grained cleavable and granular masses

Question 18

Galena cleavage

Answer 18

perfect cubic 001

Question 19

Galena hardness

Answer 19

2.5

Question 20

Galena specific gravity

Answer 20

7.4 to 7.6

Question 21

Galena color

Answer 21

bright metallic lead gray, streak lead gray

Question 22

Galena occurrence

Answer 22

• common metallic sulfide found in veins assoc with calcite, qaurtz, barite, fluorite, anglesite, cerussite, chalcopyrite, marcasite and sphalerite
• in contact metamorphism
• in pegmatites

Question 23

Galena remarks

Answer 23

good cubic cleavage, high specific gravity, soft, lead gray color and streak

Question 24

how to distinguish galena from stibnite?

Answer 24

cubic cleavage, high specific gravity and darker color

Question 25

sphalerite formula

Answer 25

ZnS

Question 26

sphalerite crystal form

Answer 26

• isometric, common: tetrahedron, dodecahedron, and cube
• crystals complex and malformed or in rounded aggregates
• cleavable masses, coarse to fine granular
• compact, botryoidal, cryptocrystalline

Question 27

sphalerite cleavage

Answer 27

dodecahedral 001 perfect
(some too fine grained to show cleavage)

Question 28

sphalerite hardness

Answer 28

3.5 to 4

Question 29

sphalerite specific gravity

Answer 29

3.9 to 4.1

Question 30

sphalerite color

Answer 30

• nonmetallic, submetallic, subresinous, adamantine, transparent to translucent
• pure: colorless
• almost pure: green
• commonly: yellow, brown to black
• increase in iron: darkens also red (ruby zinc)

Question 31

sphalerite occurrence

Answer 31

• most common ore mineral of zinc, widely distributed
• similar to galena, commonly assoc with

Question 32

sphalerite remarks

Answer 32

striking resinous luster, perfect dodecahedral cleavage, hardness

Question 33

how can you distinguish the dark variety of sphalerite?

Answer 33

black jack, reddish brown streak, lighter than the massive form of the mineral