1. The Clay Minerals J.P. Brandenburg Geosci 284 www.cactuspro.com/images/substrat_vermiculite.jpg

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

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

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

5. 3. Chemistry Alumina Octahedron

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

7. 3. Common Examples Micas (Muscovite, Biotite, Phlogopite) – mostly silica sheets http://www.pitt.edu/~cejones/GeoImages/1Minerals/1IgneousMineralz/Micas/Muscovite.JPG Clay Minerals – silica and alumina sheets Kaolinite www.soes.soton.ac.uk/resources/collection/minerals/minerals/images/M29-Kaolinite.jpg Kaolinite Chlorite http://www.minersoc.org/pages/gallery/claypix/

8. 4. Clay minerals in rocks Shale - Sedimentary http://www.biota.org/conf97/jpgs/shale1o.jpg Slate - Metamorphic Mica (Muscovite) in granite - Igneous http://www.minerals.cc http://resourcescommittee.house.gov/subcommittees/emr/usgsweb/photogalle ry/images/Slate%202_jpg.jpg

9. 5. Some Economic Uses http://www.vermontstone.com Slate as a building material www.cactuspro.com/images/substrat_vermiculite.jpg Vermiculite as a soil conditioner* *and for insulation www.gerdenhealth.com A variety of clay minerals are used for ceramics http://www.joepicassos.com/potters_wheel.html

10. 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.

11. 7. Environmental Hazards – Swelling Clay http://www.jansenkiener.com/Forensic%20Photos.htm 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

12. 8. Environmental Hazards – Mass Movement www.cnn.com www.landslides.usgs.gov http://www.swgfl.org.uk/jurassic/coastal/bowlease.jpg * 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.