mineral

Agate geode fragment

Banded chalcedony (microcrystalline SiO₂), lining a geode cavity

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; white to translucent chalcedony surrounds a dark, glossy interior, with a waxy-to-glassy luster and no prominent cleavage. The specimen appears to be a broken geode section, though its exact mineral contents are not clear from the image.

Identified October 1, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich groundwater deposited chalcedony in a cavity within volcanic rock; the cavity and deposits may be millions of years old. Agate geodes form in many regions and geological ages.

Uses & applications

Small pieces are used for collecting, lapidary work, and decorative displays; larger agate sections may be polished for ornaments or jewelry.

Geological facts

Agate is a cryptocrystalline variety of quartz; its fine-grained fibers can form distinctive bands, although banding is not obvious here.

Field identification & locations

Look for a hard, curved chalcedony rind and a former hollow interior, often lined with crystals. Common sources include Brazil, Uruguay, Mexico, and the western United States; this appears to be a modest geode fragment.