mineral
Likely botryoidal quartz or calcite cluster
Quartz (SiO₂) or calcite (CaCO₃); exact identification requires hardness and acid tests
AI-generated identification · may be incorrectTranslucent 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.
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Physical properties
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.
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.
