mineral

Polished agate slice

Chalcedony (microcrystalline quartz, SiO₂) with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent orange-red, cream, and brown banding; vitreous to waxy luster; cryptocrystalline quartz with no visible cleavage; specific gravity about 2.60–2.65. The specimen appears cut and highly polished, possibly edge-lit to enhance translucency.

Identified August 19, 2026More mineral →

Explore Polished agate slice in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Agate forms when silica-rich groundwater fills cavities in volcanic rocks, depositing concentric layers of chalcedony over long periods, commonly during the Cenozoic or older volcanic episodes. Iron oxides produce the orange-red coloration.

Uses & applications

Used for cabochons, jewelry, display slices, carvings, bookends, and ornamental objects; durable polished agate is also used for small industrial and decorative components.

Geological facts

Agate is a variety of chalcedony distinguished by banding, though some bands may be extremely subtle. Heat treatment or dyeing can intensify orange and red colors, so laboratory testing may be needed to confirm natural coloration.

Field identification & locations

Identify by translucent layered chalcedony, quartz-like hardness, waxy luster, and resistance to scratching by steel. Common sources include Brazil, Uruguay, Madagascar, India, Mexico, and the United States.