Clay minerals - hydrous aluminum silicates in phyllosilicate (sheet silicate) structures
Some irresistible geodes(for now all from Bill the Eggman-Flickr-couldn't stop looking!)
Demantoid variety of Andradite
Sand under microscope
Diatomaceous earth, diatomite
Alkali Feldspar in Granite Pegmatite Gallery of Feldspars A pegmatite vein in a large commemorative boulder displays the excellent cleavage of alkali feldspar (most likely orthoclase), along with gray quartz and a little white plagioclase. Plagioclase, the least stable of these three minerals under surface conditions, is highly weathered in this exposure.
Gneiss is a high grade metamorphic rock, meaning that it has been subjected to higher temperatures and pressures than schist. It is formed by the metamorphosis of granite, or sedimentary rock. Gneiss displays distinct foliation, representing alternating layers composed of different minerals. However, unlike slate and schist, gneiss does not preferentially break along planes of foliation because less than 50% of the minerals formed during the metamorphism are aligned in thin layers. Because of th