Editing Cristobalite (section)

== Occurrence ==
Cristobalite occurs as white octahedra or [[spherulite]]s in acidic volcanic rocks and in converted diatomaceous deposits in the [[Monterey Formation]] of the US state of California and similar areas.

The micrometre-scale spheres that make up precious [[opal]] exhibit some X-ray diffraction patterns that are similar to that of cristobalite, but lack any long-range order so they are not considered true cristobalite. In addition, the presence of structural water in opal makes it doubtful that opal consists of cristobalite.<ref>{{cite journal |author=Deane K. Smith |year=1998 |title=Opal, cristobalite, and tridymite: Noncrystallinity versus crystallinity, nomenclature of the silica minerals and bibliography |url=http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8512817 |journal=Powder Diffraction |volume=13 |issue=1 |pages=2–19 |bibcode=1998PDiff..13....2S |doi=10.1017/S0885715600009696 |s2cid=97394861|url-access=subscription }}</ref><ref>{{cite web |title=Silica, Crystalline - Overview &#124; Occupational Safety and Health Administration |url=https://www.osha.gov/dsg/topics/silicacrystalline/smithdk/pdf/nomenc.pdf |archive-url=https://web.archive.org/web/20160304134008/https://www.osha.gov/dsg/topics/silicacrystalline/smithdk/pdf/nomenc.pdf |archive-date=2016-03-04 |website=www.osha.gov}}</ref>

Cristobalite is visible as the white inclusions in ''[[snowflake obsidian]]'', a volcanic glass.