Rock Identifier
Polished honey/brown agate (likely carnelian chalcedony) (Microcrystalline quartz, SiO₂; chalcedony with iron-oxide coloration) — mineral
mineral

Polished honey/brown agate (likely carnelian chalcedony)

Microcrystalline quartz, SiO₂; chalcedony with iron-oxide coloration

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent honey, orange-brown, cream, and gray colors; waxy to vitreous luster; cryptocrystalline quartz with no cleavage and conchoidal fracture. The rounded surface indicates tumbling or polishing.

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Physical properties

Hardness 6.5–7 Mohs; translucent honey, orange-brown, cream, and gray colors; waxy to vitreous luster; cryptocrystalline quartz with no cleavage and conchoidal fracture. The rounded surface indicates tumbling or polishing.

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, commonly producing layered chalcedony and agate; iron oxides create the orange-brown tones. Most specimens formed during Cenozoic to older volcanic episodes, depending on locality.

Uses & applications

Used for cabochons, carvings, ornamental objects, and inexpensive jewelry; attractive polished pieces are popular among collectors.

Geological facts

Agate is a variety of banded or patterned chalcedony, while carnelian is orange-red chalcedony; specimens can grade continuously between them.

Field identification & locations

Identify by its translucent waxy appearance, very fine texture, conchoidal fracture, and inability to scratch with a steel knife; it should scratch glass. Common sources include Brazil, Uruguay, India, Madagascar, Mexico, and the western United States.