Rock Identifier
Purple chalcedony or lavender quartz (Cryptocrystalline quartz, SiO₂ (likely chalcedony; identification uncertain from photograph)) — mineral
mineral

Purple chalcedony or lavender quartz

Cryptocrystalline quartz, SiO₂ (likely chalcedony; identification uncertain from photograph)

AI-generated identification · may be incorrect

Pale lavender-purple, translucent to opaque, with a waxy to vitreous luster and irregular fracture; quartz hardness is about 7 Mohs, with no cleavage and specific gravity near 2.6. The rough surface and fibrous-looking zones are consistent with chalcedony, though lepidolite or fluorite are possible alternatives.

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Physical properties

Pale lavender-purple, translucent to opaque, with a waxy to vitreous luster and irregular fracture; quartz hardness is about 7 Mohs, with no cleavage and specific gravity near 2.6. The rough surface and fibrous-looking zones are consistent with chalcedony, though lepidolite or fluorite are possible alternatives.

Formation & geological history

Forms when silica-rich groundwater fills cavities or fractures in volcanic rocks, commonly as low-temperature silica deposits. Its exact geological age depends on the host rock and cannot be determined visually.

Uses & applications

Used as a lapidary material for cabochons, carvings, beads, and ornamental pieces; massive rough specimens are mainly collector materials.

Geological facts

Natural lavender chalcedony is uncommon, and purple color may result from trace manganese, iron, or irradiation; some commercial material is dyed or enhanced.

Field identification & locations

Check for a smooth waxy fracture, hardness sufficient to scratch glass, and lack of obvious cleavage; a streak, specific-gravity test, and magnification help distinguish it from fluorite, glass, and dyed stone. Common sources include Brazil, Uruguay, Madagascar, and Namibia.