GEOL 104 Lecture : GEOL 104 Lect3
17 Feb 2012
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Document Summary
98% of earth"s minerals are oxygen, silicon, aluminium, iron, calcium, sodium, Many minerals contain the most abundant elements: silicon and oxygen. Silica = silicon + oxygen (e. g. quartz = sio2) Silicates = group of minerals containing silica (e. g. kalsi3o8 = orthoclase) The basic building block of all the silicate minerals is the silicon-oxygen tetrahedron, a negatively charged ion group sio4. It is possible for the silicon-oxygen tetrahedron to become a double tetrahedron when a single oxygen joins to two silicons, which in turn are joined to three oxygen each, so then we get si2o7. The more oxygen"s are shared, the more the ratio changes(reduces) Pyroxene is a group of minerals of single chains. It has 2 cleavage chains of 90 degrees. When trying to identify it, look for something that looks like a series of stairs. It has 2 directions of cleavage at 90degrees. Silicates may also be classified by chemical groups: Two directions of cleavage that meet at 90degrees.
