mineral

Agate

Chalcedony (Silicon Dioxide, SiO2)

Hardness: 6.5–7 (Mohs scale); Color: Translucent white, gray, with reddish/orange iron staining; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Translucent white, gray, with reddish/orange iron staining
Luster: Waxy to vitreous

Identified April 8, 2026More mineral →

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Physical properties

Hardness: 6.5–7 (Mohs scale); Color: Translucent white, gray, with reddish/orange iron staining; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture).

Formation & geological history

Formed in cavities within volcanic or sedimentary rocks where silica-rich groundwater precipitates over time. This specimen shows a waxy, chalcedony-like appearance common in hydrothermal deposits.

Uses & applications

Used primarily in lapidary work for cabochons, jewelry, and decorative carvings. Industrially used for precision mortars and pestles due to its hardness and chemical resistance.

Geological facts

Agate is a variety of chalcedony distinguished by its translucency and often its banded patterns. The red spots seen here are likely iron oxide (hematite) inclusions.

Field identification & locations

Identify in the field by its waxy luster, conchoidal (shell-like) fracture, and inability to be scratched by a steel knife. Commonly found in gravel beds or volcanic regions.