sulfides 5-8 SET 2

Question 1

chalcopyrite formula

Answer 1

CuFeS2

Question 2

chalcopyrite crystal form

Answer 2

• tetragonal, tetrahedral bc of disphenoid 112
• usually massive

Question 3

chalcopyrite cleavage

Answer 3

none. brittle

Question 4

chalcopyrite hardness

Answer 4

3.5 to 4

Question 5

chalcopyrite specific gravity

Answer 5

3.1 to 3.4

Question 6

chalcopyrite color

Answer 6

metallic. brass yellow
tarnished: bronze or iridescent
greenish black streak

Question 7

chalcopyrite occurrence

Answer 7

• important copper ore mineral
• low temp hydrothermal veins, found with galena, sphalerite and dolomite
• high temp deposits with pyrrhotite and pentlandite
• primary mineral of PCDs
• primary constituent of igneous rocks, in pegmatites
• in contact metamorphic deposits
• disseminated in metamorphic schist

Question 8

chalcopyrite remarks

Answer 8

brass yellow color, greenish black streak

Question 9

how to differentiate pyrite and chalcopyrite

Answer 9

chalco is softer than steel knife. it’s softer

Question 10

how to differentiate pyrite and gold

Answer 10

chalco is britte, gold is malleable

Question 11

pyrrhotite formula

Answer 11

(Fe(1-x)S)x; x=0-0.2

Question 12

pyrrhotite crystal form

Answer 12

• hexagonal for high temp, uncommon crystals
• usually massive granular

Question 13

pyrrhotite cleavage

Answer 13

none

Question 14

pyrrhotite hardness

Answer 14

4

Question 15

pyrrhotite specific gravity

Answer 15

4.58 to 4.65

Question 16

pyrrhotite color

Answer 16

metallic opaque, brownish bronze, black streak

Question 17

pyrrhotite occurrence

Answer 17

• often disseminated grains in basic igneous rocks, such as norites
• in sulfide ore deposits assoc with pentlandite, chalcopyrite, and other sulfides

Question 18

what is a special characteristic of pyrrhotite

Answer 18

magnetism: intense and variable. easily attracted to magnets, but less magnetic than magnetite

Question 19

pyrrhotite remarks

Answer 19

massive variety assoc with pentlandite

Question 20

how to tell pyrrhotite from chalcopyrite

Answer 20

pyrrhotite is brownish bronze and is magnetic, chalco is brass yellow and is not

Question 21

how to tell pyrrhotite from pyrite

Answer 21

pyrrhotite id brownish bronze, pyrite is pale brass yellow, also pyrite is harder

Question 22

pentlandite formula

Answer 22

(Fe,Ni)9S8

Question 23

pentlandite crystal form

Answer 23

• isometric, mostly massive
• granular aggregates with octahedral parting

Question 24

pentlandite cleavage

Answer 24

none. octahedral parting on 111

Question 25

pentlandite hardness

Answer 25

3.5 to 4

Question 26

pentlandite specific gravity

Answer 26

4.6 to 5

Question 27

pentlandite color

Answer 27

metallic opaque yellowish bronze. light bronze brown streak

Question 28

pentlandite occurrence

Answer 28

- major nickel ore mineral - in basic igneous rocks assoc with nickel sulfides, pyrrhotite and chalco - probably formed by magmatic segregation

Question 29

pentlandite remarks

Answer 29

- commonly assoc with pyrrhotite, closely resembles

Question 30

how to distinguish pentlandite from pyrrhotite

Answer 30

pentlandite has octahedral parting and not magnetic

Question 31

how to detect presence of nickel in pentlandite

Answer 31

with dimethylglioxime. if this powder is dissolved in some water on pentlandite sample, scarlet coloration forms

Question 32

covellite formula

Answer 32

CuS

Question 33

covellite crystal form

Answer 33

- rarely tabular hexagonal crystals - usually massive as coatings or disseminations thru other copper minerals

Question 34

covellite cleavage

Answer 34

perfect basal 001

Question 35

covellite hardness

Answer 35

1.5 to 2

Question 36

covellite specific gravity

Answer 36

4.6 to 4.76

Question 37

covellite color

Answer 37

metallic opaque, also often iridescent. indigo blue or darker. lead gray to black streak

Question 38

covellite occurrence

Answer 38

- commonly found in most copper ore deposits as supergene mineral - found with other copper mineral and derived from them thru alteration, mainly chalcocite, bornite, chalcopyrite and enargite

Question 39

covellite remarks

Answer 39

- indigo blue color - its micaceous cleavage yielding flexible plates - association with other copper minerals