mineral

Chalcedony (Yellow Jasper or Agate)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Yellow-brown, tan, or honey-colored; Luster: Waxy to vitreous; Crystal structure: Hexagonal (trigonal); Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.65.

Hardness: 6
Color: Yellow-brown, tan, or honey-colored
Luster: Waxy to vitreous

Identified June 19, 2026More mineral →

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Physical properties

Formation & geological history

Formed via the precipitation of silica from groundwater in volcanic cavities, sedimentary rocks, or hydrothermal veins. This process occurs over millions of years, often resulting in banded (agate) or solid (jasper) forms.

Uses & applications

Used in lapidary work for making cabochons, beads, and tumbled stones. Also used historically for tools (arrowheads) due to its hardness and sharp fracture edges.

Geological facts

Chalcedony has been used as a gemstone since the Bronze Age. The name likely derives from the ancient Greek town of Chalcedon in Asia Minor. It is considered a 'cryptocrystalline' form of quartz, meaning the crystals are too small to see with a microscope.

Field identification & locations

Identify in the field by its smooth, waxy texture and inability to be scratched by a steel knife. Look for it in riverbeds, glacial deposits, and volcanic field areas. Wetting the stone reveals the inner color and translucency.

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

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Metamorphic

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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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mineral