cristobalite

[kri-stoh-buh-lahyt]
noun Mineralogy.
a polymorph of quartz occurring in volcanic rock in the form of colorless, translucent crystals.

Origin:
1885–90; named after San Cristóbal, a hill near Pachuca de Soto, Mexico; see -ite1

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cristobalite (krɪsˈtəʊbəˌlaɪt)
 
n
a white microcrystalline mineral consisting of silica and occurring in volcanic rocks. Formula: SiO2
 
[C19: from German, named after Cerro San Cristóbal, Mexico, where it was discovered]

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Encyclopedia Britannica
Encyclopedia

cristobalite

the stable form of silica (silicon dioxide, SiO2) between its melting point of 1,728 C (3,142 F) and 1,470 C (2,678 F), below which tridymite is the stable form. Cristobalite has two modifications: low-cristobalite, which occurs naturally up to 268 C (514 F) but is not stable; and high-cristobalite, which occurs above 268 C but is only stable above 1,470 C. Natural low-cristobalite usually occurs in sub-microcrystalline masses (see opal) or fibrous to columnar spherulites (see lussatite) in igneous rocks. Cristobalite has the same chemical composition as coesite, stishovite, quartz, and tridymite but has a different crystal structure. For detailed physical properties, see silica mineral (table)

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Example sentences
Some volcanic rock contains cristobalite and tridymite.
Cristobalite and tridymite can be found in volcanic rocks and soils.
Three samples were collected for quartz, cristobalite, and total particulate.
Cristobalite and tridymite are two other forms of crystalline silica.
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