A chemical compound also known as silicon dioxide (SiO2). Silica is the most common element in the earth’s crust and can be a main component of many rock types, such as quartz.
"Rounded and fine-grained eolian sand sample from the Gobi Desert" by Siim Sepp is licensed under CC BY-NC-SA.
A01 The Blessing Way (01-07) p. 67
Encyclopædia Britannica Online N.d. silica. http://www.britannica.com/EBchecked/topic/544154/silica, accessed October 15, 2014.
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