metamorphic
Milky Quartz in Gneiss
Quartzite / Foliated Gneiss containing SiO2
Hardness: 7 (Mohs), Color: White to greyish-blue, Luster: Vitreous to greasy, Structure: Microcrystalline and foliated, Cleavage: Indistinct/Conchoidal fracture
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Physical properties
Hardness: 7 (Mohs), Color: White to greyish-blue, Luster: Vitreous to greasy, Structure: Microcrystalline and foliated, Cleavage: Indistinct/Conchoidal fracture
Formation & geological history
Formed under high temperature and pressure during regional metamorphism. Often found in the Virginia Piedmont and Blue Ridge provinces, dating from the Proterozoic to Paleozoic eras.
Uses & applications
Primarily used as construction aggregate and road metal; high-purity quartz can be used in glassmaking and electronics.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. This specimen shows a mix of milky quartz with a darker, foliated metamorphic host rock typical of the Virginia Fall Line.
Field identification & locations
Identify by its inability to be scratched by steel and its lack of reaction to acid. Common across the US East Coast in riverbeds and eroded mountain soils.
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