Spherulite
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Mineral NameSpherulite
Chemical FormulaSiO2
Mohs Hardness7
Crystal Systemtrigonal
Lustervitreous
Streak Colorwhite
Cleavagenone
Fractureconchoidal
Specific Gravity2.65
Colorswhite, gray, pink, red, brown, black
Transparencytranslucent
Type LocalityCommon worldwide in volcanic regions
Mineral GroupSilicates
Usescollector, ornamental stone
Associated Mineralsvolcanic glass, feldspar, quartz, cristobalite
Raritycommon
Description
This microscopic image displays a spherulite, characterized by a radiating, fan-like growth of white to bluish-white fibrous crystals under polarized light, exhibiting a distinct extinction cross.
Geological Context
Spherulites typically form by rapid crystallization from viscous silica-rich melts, such as rhyolitic lavas and obsidians, or through the devitrification of volcanic glass.
