mineral

Quartz geode or druzy quartz nodule

Quartz, silicon dioxide (SiO₂), likely iron-oxide-stained chalcedony/quartz

AI-generated identification · may be incorrect

White to translucent quartz crystals with a brown-orange iron-oxide coating; vitreous luster, hardness 7 Mohs, hexagonal crystal structure, no cleavage, conchoidal fracture, and specific gravity about 2.65.

Identified September 22, 2026More mineral →

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Physical properties

Formation & geological history

Likely formed when silica-rich fluids filled a cavity in volcanic rock, depositing chalcedony and later quartz crystals; iron-bearing fluids produced the rusty staining. Exact geological age cannot be determined from the photograph.

Uses & applications

Used as a decorative and lapidary specimen, in jewelry, and for mineral collecting; small common pieces have modest value.

Geological facts

The brown material is probably goethite or limonite rather than part of the quartz itself. A fresh broken surface and strong glassy sparkle help distinguish quartz from calcite.

Field identification & locations

Common in volcanic cavities and hydrothermal deposits worldwide, especially Brazil, Uruguay, Mexico, and the western United States. Test with a steel file or glass: quartz should scratch glass and resist a steel blade; acid reaction would suggest calcite instead.