igneous
Quartz-rich pegmatite or quartz vein rock
Massive quartz (SiO₂), likely with feldspar and mica alteration
AI-generated identification · may be incorrectWhite to gray, coarse and irregularly crystalline with vitreous to dull luster; quartz hardness ~7 Mohs, no cleavage, conchoidal fracture, and specific gravity ~2.65. Brown coloration likely comes from iron-oxide staining or weathered mica/feldspar.
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Physical properties
White to gray, coarse and irregularly crystalline with vitreous to dull luster; quartz hardness ~7 Mohs, no cleavage, conchoidal fracture, and specific gravity ~2.65. Brown coloration likely comes from iron-oxide staining or weathered mica/feldspar.
Formation & geological history
Most likely formed from silica-rich hydrothermal fluids or the late-stage melt of a granitic pegmatite, crystallizing in fractures several hundred million to billions of years ago depending on locality. The rough surface reflects weathering and mineral alteration.
Uses & applications
Quartz-rich rock is used for silica, glass, ceramics, abrasives, countertops, and aggregate; attractive pieces may be collected as cabinet specimens. It is generally unsuitable for jewelry unless clear quartz crystals are present.
Geological facts
Quartz commonly intergrows with feldspar and mica in pegmatites and veins. Iron oxides can produce yellow, tan, or reddish coatings without changing the quartz itself.
Field identification & locations
Identify it by its very hard, glassy grains that resist scratching by a steel knife and do not fizz with dilute acid; feldspar is softer and shows cleavage. Common in granitic terrains worldwide, especially pegmatite districts.
