The Clay Minerals J.P. Brandenburg Geosci 284

1. Chemistry O -2 Si +4 O -2 Silica IonNet Charge = -4 Silica Tetrahedron Clays: Network of silca ions with shared oxygens

2. Chemistry Sheet has a negative charge Large Cation (+) Large Cations: typically Mg, Na, Ca +

3. Chemistry “Alumina” Ion OH - Al +3 OH - Net Charge = -3 Alumina Octahedron OH - Al +3 OH -

3. Chemistry Alumina Octahedron

5. Chemistry: Clay Layering Tetrahedral Layer (Silica) Octahedral Layer (Alumina)

3. Common Examples Micas (Muscovite, Biotite, Phlogopite) – mostly silica sheets Clay Minerals – silica and alumina sheets Kaolinite Kaolinite Chlorite

4. Clay minerals in rocks Shale - Sedimentary Slate - Metamorphic Mica (Muscovite) in granite - Igneous ry/images/Slate%202_jpg.jpg

5. Some Economic Uses Slate as a building material Vermiculite as a soil conditioner* *and for insulation A variety of clay minerals are used for ceramics

6. Some Economic Uses - Local The (now defunct) Grand Ledge Clay Products Company from Dorr and Eschman, Geology of Michigan, 1970 Pennsylvanian age shale was historically quarried in mid- Michigan for use in the local ceramics industry.

7. Environmental Hazards – Swelling Clay From Nelson and Miller 1982 Foundation damage High risk areas * Hazards arise from the natural ability of some clays to absorb large amounts of water

8. Environmental Hazards – Mass Movement * Although other factors such as heavy rainfall are also important, a high clay content in soil can elevate the risk of landslides in steep terrain.