mineral

Weathered agate or chalcedony nodule

Microcrystalline quartz (SiO₂), likely agate/chalcedony with iron-oxide staining

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; white, gray, tan, and brown coloration; waxy to dull luster; cryptocrystalline quartz with no visible cleavage and conchoidal fracture. The irregular surface appears naturally weathered or partially polished.

Identified August 9, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich groundwater deposited microcrystalline quartz in cavities or fractures, commonly in volcanic rock; iron oxides produced the brown staining. Exact geological age cannot be determined from the image.

Uses & applications

Used as an ornamental stone, cabochon, lapidary material, and collector specimen; non-gem-quality pieces have little industrial value.

Geological facts

Agate is defined by fine banding, while massive chalcedony may lack obvious bands; the pale, mottled appearance could also represent a silicified fossil or mineralized cavity filling.

Field identification & locations

Common in volcanic terrains, river gravels, and weathered nodules worldwide, especially Brazil, Uruguay, Mexico, the western United States, and Australia. Confirm with a scratch test against glass and inspect for translucent banding; avoid testing if valuable.