mineral

Quartz-rich geode or vuggy quartz rock

Quartz (SiO₂), likely with minor iron oxides and possibly calcite or feldspar

AI-generated identification · may be incorrect

White to translucent, vitreous to sugary luster, irregular vugs lined with small quartz crystals; Mohs hardness 7, no cleavage, conchoidal fracture, specific gravity about 2.65. The brown coating is likely iron-oxide-stained host rock.

Identified September 4, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich groundwater filled cavities and fractures in volcanic or sedimentary host rock, depositing quartz during cooling or later hydrothermal alteration. Exact geological age and locality cannot be determined from the image.

Uses & applications

Common specimens are used for collecting, lapidary work, and decorative objects; clear crystals may have modest jewelry value. Quartz is also important industrially in glass, electronics, and abrasives.

Geological facts

The cavity is a vug or small geode, and the milky appearance results from microscopic fluid inclusions or fractures. Acid testing can help distinguish associated calcite, which effervesces in dilute hydrochloric acid.

Field identification & locations

Look for hardness sufficient to scratch glass, translucent edges, and crystal faces lining cavities; quartz will not fizz in dilute acid. Common worldwide, especially in Brazil, Uruguay, Mexico, the United States, and hydrothermal vein districts.