Cristobalite
Image: Robert M. Lavinsky (CC BY-SA 3.0)
Mineral NameCristobalite
Chemical FormulaSiO2
Mohs Hardness6.5
Crystal Systemtetragonal
Lustervitreous
Streak Colorwhite
Cleavagenone
Fractureconchoidal to uneven
Specific Gravity2.27
Colorswhite, gray, colorless, yellowish
Transparencytransparent to translucent
Type LocalityCoso Hot Springs deposit, Coso Hot Springs, Inyo County, California, USA
Mineral GroupSilicates
Usesindustrial (refractories, abrasives), collector
Associated Mineralsobsidian, tridymite, quartz, opal, zeolites
Rarityuncommon
Description
The image displays a specimen of white to off-white cristobalite, exhibiting a botryoidal or mammillary habit with rounded, somewhat translucent masses.
Geological Context
Cristobalite is a high-temperature polymorph of silica, typically forming in volcanic rocks such as obsidian or rhyolite, or in hot spring deposits, often as a devitrification product of volcanic glass.
