metamorphic
Tumbled quartz-rich stone, likely iron-stained quartzite
Quartzite, predominantly SiO₂, with iron-oxide staining and possible mica/minor feldspar
AI-generated identification · may be incorrectHardness about 7 Mohs; tan, brown, and gray coloration; vitreous to dull luster; massive, granular texture with no obvious cleavage and irregular fracture. The rounded edges indicate natural abrasion or tumbling.
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Physical properties
Hardness about 7 Mohs; tan, brown, and gray coloration; vitreous to dull luster; massive, granular texture with no obvious cleavage and irregular fracture. The rounded edges indicate natural abrasion or tumbling.
Formation & geological history
Quartzite forms when quartz-rich sandstone is compacted and recrystallized during metamorphism, commonly in Precambrian to younger mountain belts. Iron oxides likely produced the rusty brown surface colors through weathering and groundwater alteration.
Uses & applications
Used as crushed aggregate, road stone, building stone, and decorative material; attractive pieces may be collected or used in lapidary work. This small specimen has limited commercial value.
Geological facts
Quartzite is notably resistant to weathering and can form ridges and durable resistant landscapes. A simple glass-scratch test can help distinguish it from softer brown sedimentary rocks, though it may damage the specimen.
Field identification & locations
Look for a very hard, quartz-granular stone that commonly scratches glass and does not fizz with dilute hydrochloric acid. Common sources include the Appalachian Mountains, Rocky Mountains, India, Brazil, and Scandinavia.
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