mineral

Agate (specifically a small Chalcedony nodule)

Agate (Cryptocrystalline variety of Quartz, SiO2)

Hardness: 6.5–7 on the Mohs scale. Color: Translucent tan, honey, or grayish with faint banding. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline/cryptocrystalline). Specific gravity: 2.58–2.64.

Hardness: 6
Color: Translucent tan, honey, or grayish with faint banding
Luster: Waxy to vitreous

Identified March 7, 2026More mineral →

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Physical properties

Formation & geological history

Formed by the deposition of silica from groundwater in the cavities (vesicles) of igneous rocks or sedimentary voids. Often associated with volcanic activity ranging from millions to hundreds of millions of years old.

Uses & applications

Used primarily for lapidary work, jewelry (cabochons), ornamental carvings, and mechanical tool bearings due to its toughness and hardness.

Geological facts

Agate is one of the oldest materials used in human history for jewelry, dating back to ancient Greece and Egypt. Every agate is unique, with no two pieces sharing the exact same internal patterns.

Field identification & locations

Identify in the field by its translucency (light passes through it), waxy texture when wet, and lack of visible crystalline faces. Commonly found in riverbeds, lake shores (like Lake Superior), and volcanic gravels.

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sedimentary

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Mineral/Rock

Banded Gneiss (River Rock/Pebble)

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Metamorphic Rock

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