mineral

Tumbled Agate

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Gray, white, and brown translucent bands; Luster: Vitreous to waxy (when polished); Crystal Structure: Trigonal (Microcrystalline); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.58-2.64

Hardness: 6
Color: Gray, white, and brown translucent bands
Luster: Vitreous to waxy (when polished)

Identified July 19, 2026More mineral →

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Physical properties

Formation & geological history

Formed in volcanic and metamorphic rocks as silica-rich groundwater fills gas cavities (vesicles) or cracks. As it cools and chemicals deposit in layers, the characteristic banding forms. Age varies from millions to billions of years depending on the host rock formation.

Uses & applications

Used primarily for jewelry (beads, cabochons), home decor, tumbled pocket stones, and industrial burnishing tools because of its hardness.

Geological facts

Agate is a variety of chalcedony. It was named by Theophrastus, a Greek philosopher, who discovered the stone along the shore line of the river Achates in Sicily.

Field identification & locations

Identify by its translucency when held to light and its characteristic concentric or planar banding. Often found in riverbeds, lake shores (like Lake Superior), and volcanic gravels. Collectors should look for unique patterns and color depth.