mineral

Agate (Chalcedony Variation)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: White, translucent milky-white, tan; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline (Trigonal); Cleavage: None (conchoidal fracture)

Hardness: 6
Color: White, translucent milky-white, tan
Luster: Waxy to vitreous

Identified February 9, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: White, translucent milky-white, tan; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline (Trigonal); Cleavage: None (conchoidal fracture)

Formation & geological history

Formed primarily in volcanic rock cavities (vugs) as silica-rich groundwater percolates and deposits microcrystalline quartz in layers. These specimens can range in age from millions to hundreds of millions of years.

Uses & applications

Commonly used for lapidary work (jewelry, beads, cabochons), ornamental bookends, mortar and pestles due to hardness, and spiritual/metaphysical collections.

Geological facts

Agate is a variety of chalcedony that is often banded. It was named by Theophrastus, a Greek philosopher, who discovered the stone along the Achates River in Sicily.

Field identification & locations

Identified by its waxy luster, translucency, and smoothness compared to the host rock. Found globally in areas with ancient volcanic activity such as Brazil, Uruguay, and the Lake Superior region of the US.

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

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Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

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