metamorphic
Tumbled purple quartzite or amethyst-bearing quartz
Quartz (SiO₂), likely quartzite; purple coloration may reflect iron impurities or minor amethyst
AI-generated identification · may be incorrectHardness about 7 Mohs; smooth, rounded, dull-to-waxy surface from tumbling; lavender-purple color with fine granular texture and no obvious cleavage. Quartzite is interlocking microcrystalline quartz with specific gravity near 2.65.
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Physical properties
Hardness about 7 Mohs; smooth, rounded, dull-to-waxy surface from tumbling; lavender-purple color with fine granular texture and no obvious cleavage. Quartzite is interlocking microcrystalline quartz with specific gravity near 2.65.
Formation & geological history
Quartzite forms when quartz-rich sandstone is recrystallized under heat and pressure, commonly during mountain-building; its exact geological age is indeterminate from the image. If the color is true amethyst, it formed from iron-bearing quartz in silica-rich hydrothermal cavities.
Uses & applications
Used as a decorative tumbled stone, cabochon, or collector specimen; quartzite is also used as durable aggregate, paving, and dimension stone.
Geological facts
The uniform purple-gray appearance and granular texture favor quartzite over transparent amethyst. Surface scratches from steel should be minimal because quartz is harder than ordinary steel.
Field identification & locations
Identify with a glass-scratch test, absence of cleavage, and granular quartz texture; acid will not react. Common sources include Brazil, India, Madagascar, and the United States.
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