mineral identification

Question 1

chromite ore mineral

Answer 1

• an oxide
• doesn’t have a metallic luster
• resinous luster
• commonly granular/octahedral
• chromite crystals often intergrow with feldspar
• chromite is generally black sometimes dark brown
• leaves a brown streak
• about same hardness as steel nail
• very weakly magnetic

Question 2

copper ore mineral

Answer 2

• variety of copper ore minerals
• in a supergene i.e. weathered surface deposit, you might see copper oxides and copper carbonates, usually bright green/blue e.g. malachite
• many copper deposits that are mined are copper sulphides
• copper iron sulphide, chalcopyrite is one of the most common.
  
  • brassy yellow
  • fairly high specific gravity/it is heavy
  • about the same hardness as copper penny
  • greenish/black streak
• bornite is also a copper iron sulphide but has a lot more copper in it
  
  • tarnishes to bright iridescent colours
  • blue/purple
  • slightly softer than chalcopyrite
  • gets scratched by copper nail
  • brown/black streak

Question 3

gold ore mineral

Answer 3

• very rare to see gold in its native gold deposit
• often gold is invisible gold, micron scale, commonly hosted in other minerals, particularly pyrite
• pyrite is a common iron sulphide
  
  • has a brassy yellow colour
  • less bright than chalcopyrite
  • has a very distinctive cubic crystal habit
  • greenish/black streak
  • about same hardness as steel
  • its crystal lattice often hosts lots of trace elements e.g. arsenic
  • the more arsenic it can host, the more gold it can host as the arsenic widens gaps in the crystal lattice
• arsenopyrite is a sulphide mineral - iron arsenic sulphide
  
  • unlike pyrite, has a grey/silver colour
  • slightly heavier/high specific gravity
  • about same hardness as pyrite - steel
  • black streak
  • doesn’t have same cubic crystal habit but an off-cubic habit
  • tarnishes to a greenish colour

Question 4

iron ore mineral

Answer 4

• hematite is a form of iron ore and is an iron oxide
  
  • red colour
  • often has a botryoidal texture - bumpy surface
  • red streak
  • relatively hard about same hardness as steel

Question 5

lead ore mineral

Answer 5

• lead sulphide - galena
  
  • silver metallic luster
  • cubic crystal habit
  • high specific gravity/heavy
  • can be scratched with a copper nail but not a fingernail which is how it can be told apart from molybdenite
  • has a grey streak

Question 6

molybdenum ore mineral

Answer 6

• molybdenite is a molybdenum sulphide
  
  • blue/silver/grey colour
  • often forms plates
  • has a greasy feel and can leave grey marks on fingers
  • very soft and can be scratched with a fingernail
  • leaves a blue/grey streak

Question 7

nickel ore mineral

Answer 7

• tends to be hosted in massive sulphide deposits
• most concentrated in pentlandite, a nickel sulphide, almost always found intergrown with pyrrhotite, a type of iron sulphide which can also contain high nickel content
• pyrrhotite
  
  • brown, bronze colour
  • metallic luster
  • has a blackish streak
  • about same hardness as a copper nail
  • weakly magnetic

Question 8

zinc ore mineral

Answer 8

• main ore mineral for zinc is sphalerite, a zinc sulphide mineral
  
  • unlike other sulphide minerals, this does not have a metallic luster
  • tends to have either a resin/adamantine(sparkly) luster
  • can be any colour but most commonly brown/black
  • doesn’t have a particularly high specific gravity
  • about the same hardness as a copper nail
  • has a pale white/yellow streak