1. Mineral Forming Processes
GCSE Geology
Mineral Forming Processes
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2. Mineral Forming Processes – S.H.R.E.C.
Minerals form in 5 different ways
Solidification
Hydrothermal Activity
Recrystallisation
Evaporation
Cementation
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3. Solidification (crystallisation) from a molten state from Lava or Magma
Cornish Granite
Shap Granite
Forms the silicate minerals making up igneous rocks and includes quartz, feldspars, micas, augite and olivine

4. Hydrothermal Activity
Groundwater is heated by igneous plutons to between 50°C and 400°C
Hot water dissolves out trace amounts of metals from large volume of rock as it travels along bedding planes, joints, laminations, faults, cleavages and pore spaces
As these hot waters cool they precipitate the metals in veins and lodes in a more concentrated form. Examples include galena (lead ore) and haematite (iron ore)
Haematite
Galena

5. Hydrothermal activity along the Mid Atlantic Ridge
Hydrothermal fluids at 350°C
Seawater at 2°C to 4°C
Chimneys can grow to over 30 metres high
Results in the formation of chimneys of massive sulphide minerals such as galena, chalcopyrite, and sphalerite

6. Metamorphic Recrystallisation
Calcite recrystallises when limestone is heated, forming marble
Heat and pressure turn clay minerals (in shale) into garnet and mica in a schist.

7. Evaporation of Salt Water
Seawater contains an average of 3.5% dissolved solids

8. Evaporation of Salt Water
As seawater evaporates the concentration of dissolved solids progressively increases

9. Evaporation of Salt Water
Salt deposits (halite) Death Valley, California
Calcite, gypsum and halite can be precipitated from solution following the evaporation of a shallow body of salt water e.g. A sea or lake

10. Precipitation as a Cement
Precipitation of minerals as a cement from pore water turns a loose sediment into sedimentary rock (lithification)
Quartz, calcite or haematite may be precipitated around existing grains filling pore spaces in sedimentary rocks
Haematite cement coating quartz grains