sedimentary

Agate (specifically Chalcedony/Banded Agate)

Silicon Dioxide (SiO2)

Hardness: 6.5–7 (Mohs scale); Color: White, translucent, and grayish-blue banding; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.60–2.65

Hardness: 6
Color: White, translucent, and grayish-blue banding
Luster: Waxy to vitreous

Identified April 13, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in cavities (vesicles) of volcanic rocks or sedimentary formations where silica-rich groundwater deposits layers over time. This specimen shows classic botryoidal-style banding indicative of secondary silica deposition.

Uses & applications

Used primarily in lapidary arts for jewelry, ornamental carvings, and as a semi-precious gemstone. Also used historically for precision bearings and mortars/pestles due to its hardness.

Geological facts

Agate is a variety of chalcedony characterized by its fineness of grain and brightness of color. It was named by Theophrastus, a Greek philosopher, who discovered the stone along the shore line of the Dirillo River in Sicily.

Field identification & locations

Identify in the field by its waxy texture, translucency when held to light, and characteristic concentric or parallel banding. This specific piece appears to be a seam agate or a fragment of a larger geode wall.

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