metamorphic
Tumbled purple quartzite
Quartzite; predominantly crystalline SiO₂ with minor iron-oxide or other mineral impurities
AI-generated identification · may be incorrectHardness about 7 Mohs; purple-brown color, fine-grained sugary texture, and dull to subtly vitreous luster. Massive, nonfoliated, and lacks visible cleavage; specific gravity approximately 2.6–2.7.
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Physical properties
Hardness about 7 Mohs; purple-brown color, fine-grained sugary texture, and dull to subtly vitreous luster. Massive, nonfoliated, and lacks visible cleavage; specific gravity approximately 2.6–2.7.
Formation & geological history
Formed when quartz-rich sandstone recrystallized under heat and pressure, typically during regional metamorphism. Its purple color likely comes from trace iron or other impurities; precise age and locality cannot be determined from the photograph.
Uses & applications
Used as durable aggregate, landscaping stone, paving, and decorative material; polished or tumbled pieces are sold for collecting and ornamental use. Common specimens generally have modest commercial value.
Geological facts
Quartzite is tougher and more resistant to weathering than its sandstone precursor. The rounded shape and uniformly smooth surface indicate mechanical tumbling rather than natural erosion.
Field identification & locations
Identify it by its granular quartz texture, high hardness, and inability to scratch with a steel knife; quartz-rich grains may sparkle on fresh surfaces. Common in metamorphic mountain belts worldwide, including Brazil, India, the United States, and Scandinavia.
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