mineral

Agate

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 Mohs; Color: Gray, yellow-brown, and white banding; Luster: Waxy to vitreous; Crystal structure: Hexagonal (cryptocrystalline); Cleavage: None; Specific gravity: 2.58-2.64

Hardness: 6
Color: Gray, yellow-brown, and white banding
Luster: Waxy to vitreous

Identified May 12, 2026More mineral →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Gray, yellow-brown, and white banding; Luster: Waxy to vitreous; Crystal structure: Hexagonal (cryptocrystalline); Cleavage: None; Specific gravity: 2.58-2.64

Formation & geological history

Formed primarily in volcanic and metamorphic rocks. It occurs as a secondary mineral in nodules or as a filling in cavities when silica-rich groundwater flows through basalt or andesite gas bubbles.

Uses & applications

Used for jewelry (cabochons, beads), decorative ornaments, mortar and pestles for chemicals, and industrial precision bearings.

Geological facts

Agate was named by Theophrastus, a Greek philosopher, who discovered the stone along the shore line of the river Achates in modern-day Sicily. It is one of the oldest healing minerals.

Field identification & locations

Identify in the field by its waxy luster, translucency when held to light, and characteristic banding or irregular inclusions. Commonly found in riverbeds and gravel pits in volcanic regions.