Silica | Defined by John Szabo (2016, p.249) as ‘a widespread chemical compound formed from silicon and oxygen, aka silicon dioxide, one of the most abundant in the earth’s crust. Silica content is used to distinguish between types of lava. See Horn silica 501 and soil types.

Bibliography

John Szabo, MS, Volcanic Wines, (Jacqui Small, 2016).