mineral

Likely botryoidal quartz or calcite cluster

Quartz (SiO₂) or calcite (CaCO₃); exact identification requires hardness and acid tests

AI-generated identification · may be incorrect

Translucent honey-brown, clustered crystals with vitreous to resinous luster and apparent drusy/botryoidal growth. Quartz hardness is 7, no cleavage; calcite hardness is 3, with prominent rhombohedral cleavage and vigorous fizz in dilute hydrochloric acid.

Identified August 25, 2026More mineral →

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Physical properties

Formation & geological history

Likely formed from mineral-rich hydrothermal or cavity-filling fluids, potentially in a geode or vug; its precise geological age and locality cannot be determined from the image.

Uses & applications

Quartz is used in glass, electronics, abrasives, and specimens; calcite is used in cement, lime, construction aggregate, and collecting. Attractive clusters may be sold as display minerals.

Geological facts

The brown color may result from iron-oxide inclusions or staining. Crystal shape is obscured by the cluster, so visual identification alone is uncertain.

Field identification & locations

Scratch a glass surface: quartz usually scratches it, while calcite does not; test calcite with dilute acid. Common sources include Brazil, Mexico, Morocco, and the United States.