Mineral formation

Minerals are Formed by: Crystallisation from a melt Crystalline interlocking texture so rarely euhedral Major minerals – quartz, feldspar, mica

Minerals are Formed by: Metamorphic Recrystallisation Crystalline interlocking texture often with overgrowths Major minerals – calcite, garnet

Minerals are Formed by: Evaporation Crystalline usually euhedral Major minerals – halite

Minerals are Formed by: Crystallisation as cement from flowing pore waters Crystalline very fine grained holds clasts together Major minerals – quartz, calcite

Minerals are Formed by: Crystallisation from hydrothermal fluids Crystalline in veins and faults crystallises out from supersaturated fluids when cools Major minerals – gangue, quartz, calcite, ores: haematite, galena

Factors that affect crystal growth Size/shape of environment Temperature Pressure Seed crystal

Size of environment Bigger the space, bigger the crystal

Temperature Longer it takes to cool (stays warm longer) the bigger the crystals can get

Pressure Changes shape/ alignment of crystals

Seed crystals Allows for a “blueprint” for crystal growth