metamorphic
Quartz-bearing metamorphic rock, likely quartzite or hornfels
Quartz (SiO₂) in a fine-grained silicate matrix; exact rock identification requires testing
AI-generated identification · may be incorrectHardness approximately 6–7 where quartz is exposed; gray-brown, granular, with white translucent quartz and a vitreous luster. The dark matrix may be mica-, feldspar-, or iron-rich; crystal structure is mostly microscopic, with no obvious cleavage in the quartz.
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Physical properties
Hardness approximately 6–7 where quartz is exposed; gray-brown, granular, with white translucent quartz and a vitreous luster. The dark matrix may be mica-, feldspar-, or iron-rich; crystal structure is mostly microscopic, with no obvious cleavage in the quartz.
Formation & geological history
Likely formed when silica-rich fluids filled fractures or when a sedimentary rock was metamorphosed by heat and pressure, probably during a Paleozoic or younger mountain-building event. The specimen’s exact age and process cannot be determined from the photograph.
Uses & applications
Primarily a collecting specimen; quartzite can be used as aggregate, building stone, or road material, while attractive quartz pockets may be cut or displayed. This piece appears too small and irregular for significant commercial use.
Geological facts
The white area appears to be massive or coarsely crystalline quartz, possibly a quartz vein or amygdule. Brown coloration may result from iron-oxide staining or weathered mafic minerals.
Field identification & locations
Commonly found in metamorphic terrains and quartz veins worldwide, including the Appalachians, western U.S., Brazil, and Australia. Quartz scratches glass and does not fizz in dilute hydrochloric acid; a hand lens can reveal quartz grains and matrix texture.
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