sedimentary

Yellow Chalcedony (Agate)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Pale yellow to deep amber (translucent); Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline (Trigonal/Monoclinic); Cleavage: None; Specific Gravity: 2.58–2.64

Hardness: 6
Color: Pale yellow to deep amber (translucent)
Luster: Waxy to vitreous

Identified June 16, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the deposition of silica from groundwater in cavities of igneous rocks or sedimentary layers. It can be found in volcanic vugs or as nodules in limestone.

Uses & applications

Used primarily in lapidary work for jewelry, cabochons, and decorative carvings. Industrially, it has been used in mortar and pestle sets due to its hardness and durability.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen with a microscope. It has been used for making tools and seals since the Bronze Age.

Field identification & locations

Identify by its waxy luster, conchoidal fracture, and translucency when held to light. Frequently found in riverbeds or volcanic regions like Brazil, India, and the Western United States.