mineral

Botryoidal chalcedony (likely druzy agate)

Microcrystalline quartz, SiO₂, with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent cream to honey-brown with reddish-brown staining, waxy luster, and sparkling drusy quartz cavities. Quartz has trigonal crystal structure and no cleavage; fracture is typically conchoidal. The rounded, bubbly texture is botryoidal.

Identified August 10, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater deposits chalcedony in cavities and fractures, commonly in volcanic rocks; later cavities may receive quartz druse and iron oxides. The specimen’s exact geological age cannot be determined from the image.

Uses & applications

Used as a lapidary stone for cabochons, carvings, and polished specimens; attractive pieces are collected as agate or chalcedony. Not generally used for construction.

Geological facts

Its rounded surface results from successive silica coatings, while the glittering cavity lining consists of tiny quartz crystals. Iron oxides create the orange, red, and brown colors.

Field identification & locations

Identify by its waxy translucence, conchoidal fracture, hardness, and botryoidal surface; a steel file should not easily scratch it. Common in volcanic regions worldwide, including Brazil, Uruguay, Mexico, India, and the western United States.