mineral

Botryoidal chalcedony (possible seam agate)

Microcrystalline quartz, SiO₂; commonly with iron-oxide and clay inclusions

AI-generated identification · may be incorrect

Typically hardness 6.5–7, waxy to dull luster, translucent white-gray with pink, brown, and cream banding or botryoidal surfaces. Quartz has a trigonal structure and no cleavage; this specimen is heavily weathered and cavity-rich.

Identified August 10, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities, fractures, or vesicles and deposits chalcedony, sometimes in layers or rounded botryoidal growths. Exact age and locality cannot be determined from the image; formation may occur in volcanic or sedimentary host rocks.

Uses & applications

Used as ornamental stone, cabochons, carvings, lapidary material, and collectible specimens; the pictured rough piece has limited commercial value.

Geological facts

The uneven rounded texture and waxy appearance are characteristic of chalcedony rather than crystalline quartz. Pink-brown coloration commonly reflects iron oxides or other mineral impurities.

Field identification & locations

Identify by its waxy luster, curved fracture, very fine grain, and resistance to scratching with a steel knife; a streak or hardness test is useful. Common sources include Brazil, Uruguay, Madagascar, Mexico, Turkey, and the western United States.