Definition of "silica" [sil•i•ca]

• A white or colorless crystalline compound, SiO2, occurring abundantly as quartz, sand, flint, agate, and many other minerals and used to manufacture a wide variety of materials, especially glass and concrete. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Grasses have a gritty compound called silica, which is contained in sand and is used to make glass."
• "And not too surprisingly (since silica is the most abundant mineral in the Earth’s crust), the coating is non-toxic and environmentally harmless."
• "It is from the silicone family, which originates from silica, which is found in granite, quartz and sand."