gemstone

Polished brown agate

Microcrystalline quartz (chalcedony), SiO₂, likely banded agate

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent brown, honey, cream, and white banding with waxy to vitreous luster. Quartz is trigonal microscopically, with no cleavage and conchoidal fracture; polishing and the elongated shape obscure natural texture.

Identified September 5, 2026More gemstone →

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Physical properties

Formation & geological history

Agate forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony in successive layers. The specimen’s geological age depends on its host lava, commonly Paleozoic to Cenozoic.

Uses & applications

Used for cabochons, carvings, ornaments, beads, and polished collectibles; agate is also used for durable decorative and industrial objects.

Geological facts

The coloration commonly comes from iron oxides and hydroxides. This appears shaped and highly polished, so its original nodule or vein form cannot be determined from the image.

Field identification & locations

Identify by testing for glassy conchoidal fracture, translucency, fine curved banding, and hardness sufficient to scratch ordinary glass; avoid acid tests. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the United States.