mineral

Quartz geode

Silica geode; predominantly microcrystalline and crystalline quartz (SiO₂), possibly with chalcedony

AI-generated identification · may be incorrect

Typically a hollow, rounded nodule with a gray-brown chalcedony rind and sparkling colorless to pale-gray quartz crystals lining the cavity. Quartz hardness is Mohs 7, vitreous luster, trigonal crystal structure, and no cleavage; the specimen appears cut or naturally broken open.

Identified September 7, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, often replacing vesicles; crystals grow inward over long periods, commonly during the Mesozoic or Cenozoic. Exact age and locality cannot be determined from the image.

Uses & applications

Used as a decorative and lapidary specimen, in jewelry, and for mineral collecting; quartz is also important industrially in glass, electronics, and abrasives.

Geological facts

The outer rind formed before the inner crystals, and the open cavity records a former gas bubble or dissolution void. Gray interiors may reflect chalcedony, clay, iron oxides, or other inclusions.

Field identification & locations

Identify by the hollow cavity, botryoidal/chalcedony rind, and inward-pointing quartz crystals; common sources include Brazil, Uruguay, Mexico, Morocco, and the United States. A locality label, crystal quality, and whether it is natural or enhanced are important for collectors.