minerals. minerals what are minerals? what types of minerals are there? how are minerals formed?...
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Minerals
MINERALS
What are minerals? What types of
minerals are there?
How are minerals formed?
Solid/Crystalline Elements or Compounds
Naturally Occurring
Rock Forming Minerals
Ore Minerals
• Haematite
• Galena
Crystallisation from a Melt
Solution (Evaporation)
• Halite
• Gypsum
• Calcite
• Quartz
• Micas
• Feldspars
• Quartz
• Feldspar
• Mica
• Garnet
• Calcite
Metamorphism (solid state)
• Garnet
• Calcite
Crystallisation as a cement from flowing
pore waters• Quartz
• Calcite
Crystallisation from Hydrothermal Fluids in Veins and Faults
• Gangue
• Quartz
• Calcite
• Ores
• Haematite
• Galena
Gangue•Calcite•Quartz
How can minerals be identified?
• Hardness
• Streak
• Cleavage/fracture
• Density/ hefting
• Lustre
• Colour
• Acid
Moh’s Scale – fingernail, copper coin, steel nail
Powder left on a porcelain tile (colour)
Planes of weakness easily broken
How heavy it is (by volume)
The way a mineral reflects light. Vitreous/Metallic/Glassy/Dull/Transparent/Translucent
Beware – some can show a range of colours
HCl will fizz in the presence of CaCO3 (calcite)
Minerals
• Mineral 1 – black colour, hardness 2.5, one good cleavage plane
• Mineral 2 – grey colour, scratches streak plate, no cleavage
• Mineral 3 – white in colour, hardness 6, 2 good cleavage planes in some crystals
• Mineral 4 – dark green/black in colour, hardness 5-6, 2 good cleavage planes at 90o
• Mineral 5 – white in colour, splits along 3 planes
Mica
Quartz
Feldspar
Augite
Halite or Calcite
Minerals
Mineral 1
White colour, hardness 6, 2 cleavage planes, vitreous.
Mineral 2
Pink colour, hardness 6, 2 cleavage planes, vitreous.
Mineral 3Colourless, scratches streak plate, no cleavage planes, vitreous.
Mineral 4
Black colour, scratched by finger nail, 1 cleavage planes.
Minerals are Formed by:
Crystallisation from a melt
Crystalline interlocking textureso rarely euhedral
Major minerals – quartz, feldspar, mica
Minerals are Formed by:
Metamorphic Recrystallisation
Crystallineinterlocking texture
often with overgrowths
Major minerals – calcite, garnet
Minerals are Formed by:
Evaporation
Crystallineusually euhedral
Major minerals – halite
Minerals are Formed by:
Crystallisation as cementfrom flowing pore waters
Crystallinevery fine grained
holds clasts together
Major minerals – quartz, calcite
Minerals are Formed by:
Crystallisation from hydrothermal fluids
Crystallinein veins and faults
crystallises out from supersaturated fluids when
coolsMajor minerals – gangue, quartz, calcite, ores: haematite, galena
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