metamorphic
Quartz–mica metamorphic rock, likely schist
Quartz–muscovite/biotite schist; predominantly SiO₂ quartz with phyllosilicate micas
AI-generated identification · may be incorrectGray-white, coarse-grained and foliated, with translucent vitreous quartz and dark micaceous patches; quartz hardness 7, mica hardness 2–3, generally low cleavage in quartz but excellent basal cleavage in mica. The specimen appears moderately weathered and iron-stained.
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Physical properties
Gray-white, coarse-grained and foliated, with translucent vitreous quartz and dark micaceous patches; quartz hardness 7, mica hardness 2–3, generally low cleavage in quartz but excellent basal cleavage in mica. The specimen appears moderately weathered and iron-stained.
Formation & geological history
Formed when quartz-rich sedimentary or igneous protolith was buried and subjected to elevated temperature and directed pressure, producing mica alignment and schistosity. Its precise age cannot be determined from the photograph; such rocks occur from Precambrian to recent mountain belts.
Uses & applications
Used locally as decorative stone, aggregate, and occasionally dimension stone; attractive pieces may be sold as educational or cabinet specimens, but it is not typically a jewelry gemstone.
Geological facts
The dark material may be biotite, chlorite, graphite, or amphibole, so exact identification requires hardness, streak, cleavage, and possibly microscopy or chemical analysis.
Field identification & locations
Look for planar foliation, glittering mica flakes, and quartz-rich layers that split irregularly along mica planes; common in metamorphic mountain belts worldwide. Approximate value: $5–$30 for a common hand specimen, or $30–$100 if unusually attractive and well documented.
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