mineral

Polished banded agate

Agate, microcrystalline quartz (SiO₂), commonly with chalcedony and trace iron oxides

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent cream, orange, and honey-brown bands; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage; specific gravity about 2.60–2.65.

Identified August 21, 2026More mineral →

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Physical properties

Hardness 6.5–7 Mohs; translucent cream, orange, and honey-brown bands; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage; specific gravity about 2.60–2.65.

Formation & geological history

Forms when silica-rich groundwater repeatedly fills cavities in volcanic rocks, depositing concentric or irregular chalcedony bands. Most specimens formed in Phanerozoic volcanic settings, though exact age depends on locality.

Uses & applications

Used for cabochons, beads, carvings, tumbled stones, ornaments, and lapidary objects; durable and attractive but generally inexpensive.

Geological facts

The banding reflects changing fluids and impurities during cavity filling, especially iron producing orange and brown colors. It is a variety of chalcedony rather than a separate mineral species.

Field identification & locations

Identify by curved or parallel translucent bands, waxy luster, and quartz-like hardness; common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the United States. A streak test is white, and it does not effervesce in dilute acid.