mineral

Chalcedony (specifically Agate or Carnelian pebble)

Chalcedony (Microcrystalline Quartz, SiO2)

Hardness: 6.5–7 (Mohs scale); Color: Yellow-orange to translucent amber; Luster: Waxy to vitreous; Crystal Structure: Trigonal/Monoclinic (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.64.

Hardness: 6
Color: Yellow-orange to translucent amber
Luster: Waxy to vitreous

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed via the deposition of silica from groundwater in cavities of volcanic rocks (lava flows) or sedimentary layers. They often occur as nodules or amygdules, appearing as water-worn pebbles after long-term erosion.

Uses & applications

Used primarily in lapidary arts for jewelry, beads, and carvings. Also used historically for hardstone carvings, seals, and as decorative gemstones.

Geological facts

Carnelian and agate pebbles have been used by humans since antiquity; they were highly prized in Ancient Egypt and Sumeria for protective amulets. The translucent quality comes from the tight interlocking of microscopic quartz fibers.

Field identification & locations

Identify in the field by its waxy texture, smooth rounded exterior (if water-worn), and lack of visible crystal grains. It will scratch glass but cannot be scratched by a steel knife. Common in riverbeds and gravel deposits in volcanic regions.

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