sulfides 5-8 SET 2 Flashcards
chalcopyrite formula
CuFeS2
chalcopyrite crystal form
- tetragonal, tetrahedral bc of disphenoid 112
- usually massive
chalcopyrite cleavage
none. brittle
chalcopyrite hardness
3.5 to 4
chalcopyrite specific gravity
3.1 to 3.4
chalcopyrite color
metallic. brass yellow
tarnished: bronze or iridescent
greenish black streak
chalcopyrite occurrence
- 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
chalcopyrite remarks
brass yellow color, greenish black streak
how to differentiate pyrite and chalcopyrite
chalco is softer than steel knife. it’s softer
how to differentiate pyrite and gold
chalco is britte, gold is malleable
pyrrhotite formula
(Fe(1-x)S)x; x=0-0.2
pyrrhotite crystal form
- hexagonal for high temp, uncommon crystals
- usually massive granular
pyrrhotite cleavage
none
pyrrhotite hardness
4
pyrrhotite specific gravity
4.58 to 4.65
pyrrhotite color
metallic opaque, brownish bronze, black streak
pyrrhotite occurrence
- often disseminated grains in basic igneous rocks, such as norites
- in sulfide ore deposits assoc with pentlandite, chalcopyrite, and other sulfides
what is a special characteristic of pyrrhotite
magnetism: intense and variable. easily attracted to magnets, but less magnetic than magnetite
pyrrhotite remarks
massive variety assoc with pentlandite
how to tell pyrrhotite from chalcopyrite
pyrrhotite is brownish bronze and is magnetic, chalco is brass yellow and is not
how to tell pyrrhotite from pyrite
pyrrhotite id brownish bronze, pyrite is pale brass yellow, also pyrite is harder
pentlandite formula
(Fe,Ni)9S8
pentlandite crystal form
- isometric, mostly massive
- granular aggregates with octahedral parting
pentlandite cleavage
none. octahedral parting on 111
pentlandite hardness
3.5 to 4
pentlandite specific gravity
4.6 to 5
pentlandite color
metallic opaque yellowish bronze. light bronze brown streak
pentlandite occurrence
- major nickel ore mineral
- in basic igneous rocks assoc with nickel sulfides, pyrrhotite and chalco
- probably formed by magmatic segregation
pentlandite remarks
- commonly assoc with pyrrhotite, closely resembles
how to distinguish pentlandite from pyrrhotite
pentlandite has octahedral parting and not magnetic
how to detect presence of nickel in pentlandite
with dimethylglioxime. if this powder is dissolved in some water on pentlandite sample, scarlet coloration forms
covellite formula
CuS
covellite crystal form
- rarely tabular hexagonal crystals
- usually massive as coatings or disseminations thru other copper minerals
covellite cleavage
perfect basal 001
covellite hardness
1.5 to 2
covellite specific gravity
4.6 to 4.76
covellite color
metallic opaque, also often iridescent. indigo blue or darker. lead gray to black streak
covellite occurrence
- 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
covellite remarks
- indigo blue color
- its micaceous cleavage yielding flexible plates
- association with other copper minerals
