mineral

Chalcedony (Commonly known as Carnelian or Agate pebble)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Translucent brownish-orange to tan. Luster: Waxy to vitreous. Crystal structure: Hexagonal (trigonal) microcrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Translucent brownish-orange to tan
Luster: Waxy to vitreous

Identified March 27, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica from groundwater in cavities of volcanic and sedimentary rocks. This specific specimen appears to be a water-worn river pebble, likely dating from the Cenozoic era or older, depending on the host formation.

Uses & applications

Used in the lapidary arts for cabochons, beads, and carvings. Historically used for making cylindrical seals and signet rings. Also used in industrial abrasive applications and stone masonry.

Geological facts

Chalcedony was highly prized in the ancient world; the Minoans used it for seal stones at the Palace of Knossos. Its 'waxy' appearance distinguishes it from common glass or coarser quartz.

Field identification & locations

Identify in the field by its translucency (light passes through edges), conchoidal fracture patterns (curved chips), and lack of visible grains. Commonly found in riverbeds, gravel pits, and coastal beaches.

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