Silicon's atomic number is 14 and its symbol is Si. Silicon is an essential compound in the semiconductor industry. This sample happens to be 99.995% pure silicon. The squares you see in the computer chip are doping material only a few atoms thick making this one of the purest samples you can easily find. Although silicon does not have a major role in animals, silicon structures are excreted by various sea sponges and microorganisms. It is also contained in various plant tissues. Silicon oxide or “silica” has been discovered in Egyptian-made glass dating back to 1500 BC. Silica is one of the best-researched compounds second only to water. Twelve different crystal forms of silica exist including jasper, onyx, flint, opal, and quartz. Silicon is the second most abundant element in the earth's crust behind oxygen. Silicon makes up a total of approximately 27% of the earth's crust by weight.