metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly microcrystalline quartz (SiO₂), with minor dark mica or amphibole and possible feldspar
AI-generated identification · may be incorrectGray to silvery, granular and sugary texture with vitreous-to-subvitreous luster; quartz hardness is Mohs 7, with no cleavage and uneven fracture. The apparent foliated or banded areas suggest minor mica-rich inclusions, so a quartz-mica schist is an alternative.
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Physical properties
Gray to silvery, granular and sugary texture with vitreous-to-subvitreous luster; quartz hardness is Mohs 7, with no cleavage and uneven fracture. The apparent foliated or banded areas suggest minor mica-rich inclusions, so a quartz-mica schist is an alternative.
Formation & geological history
Formed when quartz-rich sandstone recrystallized under moderate-to-high metamorphic pressure and temperature, commonly during mountain building. Its exact geological age cannot be determined from the photograph and depends on its source region.
Uses & applications
Used as crushed stone, aggregate, paving and decorative dimension stone; attractive pieces are collected, polished, or used in lapidary work, though this specimen is not gem grade.
Geological facts
Quartzite is commonly more resistant to weathering than its parent sandstone and often forms ridges or prominent hills. A steel file should not scratch clean quartz-rich areas, while hydrochloric acid should produce no reaction.
Field identification & locations
Likely quartzite if the grains are fused and the rock breaks across grains; visible aligned mica and easy splitting would favor quartz-mica schist. Common sources include metamorphic mountain belts worldwide; value is typically $5–$25 for a hand specimen, or up to $50–$100 for unusually attractive polished material.
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