mineral

Agate

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Brown, tan, white, and translucent gray; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline/cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Brown, tan, white, and translucent gray
Luster: Waxy to vitreous

Identified June 21, 2026More mineral →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Formed in cavities of volcanic rocks or ancient lavas where silica-rich groundwater deposited layers of microcrystalline quartz over long periods. These specimens can range from thousands to millions of years old.

Uses & applications

Widely used for jewelry, decorative carvings, bookends, and industrial uses like mortar and pestles due to its hardness and resistance to acids.

Geological facts

The banding in agates is caused by rhythmic crystallization and variations in the impurities of the silica-rich fluids. This specific specimen features 'water-line' or level banding in the center, created when gravity influences the settling of silica layers.

Field identification & locations

Identify in the field by its waxy luster when broken, translucent edges, and characteristic concentric or parallel banding. Commonly found in riverbeds, glacial tills, and volcanic regions globally, notably Brazil, Uruguay, and the Lake Superior region.