mineral

Agate slice

Chalcedony (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Translucent tan, white, and grey bands; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Translucent tan, white, and grey bands
Luster: Waxy to vitreous

Identified June 21, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Translucent tan, white, and grey bands; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.58-2.64.

Formation & geological history

Agate forms in cavities of volcanic rocks or ancient lavas. Silica-rich groundwater percolates through these voids, depositing layers of microcrystalline quartz over thousands to millions of years.

Uses & applications

Commonly used in jewelry (cabochons), interior decor (slices, coasters), and industrial mortars and pestles due to its hardness and chemical resistance.

Geological facts

The banding in agates is caused by rhythmic crystallization of silica. No two agates are exactly alike, making each slice uniquely patterned. This specific piece shows botryoidal or vuggy structures common in geode fragments.

Field identification & locations

Identify in the field by looking for translucent, banded nodules with a waxy surface. They are frequently found in gravel beds of rivers or weathered out of volcanic terrain.