There are many major clay mineral groups each with its own structure and chemistry. Individual clay particles are each leaf or flake shaped, therefore their name... PHYLLOSILICATES. These are silicates, combinations of silicon and oxygen, arranged in tetrahedrons, four-sided pyramids, with other elements combined, or in the interstices or incorporated in the flat platy structure. Phyllo is Greek for leaf, hence Phyllosilicates. In geology we are taught that clays require water to form, adapt to water in different ways, are the end product of chemical and physical weathering primarily of feldspars... including the gemstone Moonstone and the flashy high energy Labradorite. The feldspar group makes up about 80% of all crustal minerals. They are the essential minerals in all igneous rocks and most metamorphic rocks and their derivatives, the clays, make up unsurprisingly, 80 % of all sedimentary rocks... shale, mudstone, claystone. Soils which give us all life are 80% clay minerals! WIKI ARTICLE ON CLAY MINERALS Don't worry! I'll be back to help with the terminology that is particular to our quest for health AND beauty using the clays! Since the clays are flat and the outer surfaces are broken, they present more POSITIVE cation bonds to the surface than do your ORDINARY crystals used for healing and wellness. That is their secret!