Cristobalite
1 in the gallery
Cristobalite is a high-temperature polymorph of silica (SiO2) that often appears as colorless or white crystals, grains, or massive aggregates with a vitreous luster. It commonly forms in volcanic environments and within rhyolitic and obsidian-rich contexts, where rapid cooling can stabilize the cristobalite structure. Crystals can be slender and prismatic, occasionally forming delicate transparent to translucent specimens that catch light with a glassy sheen.
- Formula
- SiO2
- Rarity
- Uncommon
- Stability
- Moderately Stable
- Collector interest
- Moderate Interest
- Classification notes
- Silicate mineral; tectosilicate (framework silicate); silica group (SiO2)
Key characteristics
- Crystal system
- tetragonal
- Mohs hardness
- 6.5–7
- Specific gravity
- 2.32–2.36
- Luster
- vitreous
- Transparency
- transparent, translucent
- Color
- colorless, white, gray, yellow, brown
- Streak
- white
- Cleavage
- none
- Fracture
- conchoidal, uneven
- Crystal habit
- octahedral, druzy, granular, massive
About Cristobalite
SignificantCristobalite material has been recovered from well-known localities in the United States and India, among others, where hydrothermal and volcanic histories have preserved it in a range of habit forms. Collectors prize well-formed, gem-like crystals and well-documented association with other silica minerals. Its appearance, persistence under heat, and connection to distinctive geological settings make cristobalite a sought-after species for demonstrations of silica polymorphism and for display alongside related minerals.