mineral

Drusy quartz coating on volcanic rock

Quartz (SiO₂), likely druzy quartz on basalt or another mafic host

AI-generated identification · may be incorrect

Tiny sparkling quartz crystals form a dark gray to purple granular surface over a dense, darker rock. Quartz hardness is 7 Mohs, vitreous luster, trigonal crystal structure, and no cleavage; the host appears fine-grained and may be basaltic.

Identified September 4, 2026More mineral →

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Physical properties

Formation & geological history

Groundwater or hydrothermal fluids deposited microcrystalline quartz in cavities or along fractures, commonly during cooling or later alteration of volcanic rock. The precise age and locality cannot be determined from the image.

Uses & applications

Used as a decorative and collecting specimen; attractive drusy surfaces may be incorporated into jewelry and polished décor. The host rock has little industrial value in this form.

Geological facts

The glitter comes from many crystal faces rather than metallic particles. Purple coloration may indicate amethyst-bearing quartz or surface staining, but the image is insufficient for confident identification.

Field identification & locations

Look for a sugary, sparkly quartz surface, glassy crystal reflections, and a hard, nonmetallic coating; a scratch test should not mark quartz with a steel nail. Common examples occur in volcanic cavities worldwide, especially Brazil, Uruguay, Mexico, and Morocco.