mineral

Agate (Chalcedony)

Agate (Silicon Dioxide - SiO2)

Hardness: 6.5–7 on Mohs scale; Color: White, cream, grey-blue with possible banding; Luster: Waxy to vitreous; Crystal Structure: Trigonal/Microcrystalline; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.58–2.64

Hardness: 6
Color: White, cream, grey-blue with possible banding
Luster: Waxy to vitreous

Identified April 10, 2026More mineral →

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Physical properties

Formation & geological history

Formed in cavities (vesicles) within volcanic rocks or ancient hydrothermal veins. Silica-rich groundwater deposits layers of microcrystalline quartz over thousands of years. Often found in Cenozoic or Mesozoic volcanic deposits.

Uses & applications

Used in gemstone jewelry (cabochons), precision measurement tools (pendulums/bearings), burnishing tools, and decorative carvings.

Geological facts

Agate is uniquely characterized by its fine grain and variety of colors; it was highly valued in antiquity for making cylinder seals and amulets to protect against storms.

Field identification & locations

Identify by its waxy texture, hardness (cannot be scratched by a steel knife), and translucent edges when held to light. Often found in riverbeds or fields near volcanic mountain ranges.