Secondary minerals

Secondary minerals: Minerals that are formed, by the weathering of primary minerals are known as secondary mineral. Eg: Limonite, Gibbsite etc., and clay minerals like Kaolinite, Montmorillonite etc.,

1. Gypsum - CaSO4 .2H2O

• Forms from evaporating calcium sulfate-bearing waters

• Very soft and weathers fairly readily

• Accumulate in large quantities in semi-arid regions

• Can be both a Primary and Secondary mineral

2. Calcite - CaCO3(carbonates)

• Commonly found in limestone and Marble

• Much softer than glass; harder than fingernails

• White or colored by impurities

• Slightly soluble in water

• Effervesces in dilute HCI (release bubbles of CO2)

3. Dolomite - CaCO3 MgCO3

• Most common liming material in NC

• Similar to calcite

• Contains Mg

4. Iron oxides

• Formed through chemical weathering

• Geothite (FeOOH): gives yellow color in soils

• Hematite (Fe2O3): responsible for red coloration in soils

5. Clay Minerals (kaolinite)

• Highly colloidal

• Formed primarily from chemical weathering of primary minerals

• Ability to absorb or hold nutrient ions on their surfaces