metamorphic
Weathered quartz-rich rock, likely quartzite
Quartzite; predominantly crystalline SiO₂, possibly iron-oxide stained
AI-generated identification · may be incorrectHardness about 7 Mohs; white to honey-brown with rusty red staining, vitreous to dull luster, granular interlocking quartz crystals, and no obvious cleavage. The rough, massive texture is consistent with quartzite rather than a single quartz crystal.
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Physical properties
Hardness about 7 Mohs; white to honey-brown with rusty red staining, vitreous to dull luster, granular interlocking quartz crystals, and no obvious cleavage. The rough, massive texture is consistent with quartzite rather than a single quartz crystal.
Formation & geological history
Formed when quartz-rich sandstone was metamorphosed and recrystallized under heat and pressure, commonly during mountain-building; its exact geological age cannot be determined from the photograph. Iron-bearing groundwater likely produced the orange-brown staining.
Uses & applications
Used as crushed stone, aggregate, building stone, countertops, and decorative landscaping material; attractive pieces may be collected but are generally not gem quality.
Geological facts
Quartzite commonly breaks across quartz grains in a hard, splintery or irregular fracture and typically resists scratching by a steel knife. A streak or scratch test can help distinguish it from softer sandstone.
Field identification & locations
Common in metamorphic mountain belts worldwide, including the Appalachian and Rocky Mountains, Scandinavia, India, and Brazil. Confirm by attempting to scratch it with steel and checking whether dilute hydrochloric acid produces no reaction.
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