Mineral

Agate

Silicon Dioxide (SiO2) - Cryptocrystalline Chalcedony

Hardness: 6.5-7 on the Mohs scale. Color: Variable (this specimen shows white, translucent grey, and pale pink/red banding). Luster: Vitreous to waxy. Crystal structure: Hexagonal (cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.58-2.64.

Hardness: 6
Luster: Vitreous to waxy

Identified March 14, 2026More mineral →

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Physical properties

Formation & geological history

Formed in cavities within volcanic rocks (basalt or andesite) or sedimentary rocks. It is created when silica-rich groundwater seeps into these cavities and deposits layers of microscopic quartz crystals over long geological periods.

Uses & applications

Primary use is in jewelry, lapidary art, and ornamental carvings. Historically used for making mortars and pestles, precision balances, and burnishing tools due to its high hardness and chemical resistance.

Geological facts

Agate is named after the Achates River in Sicily where it was first discovered. It is the birthstone for September and is one of the oldest materials in human history used for decorative purposes, dating back to Ancient Greece.

Field identification & locations

Identify in the field by its waxy luster, translucency when held to light, and characteristic concentric banding or druzy quartz pockets. Commonly found in riverbeds, or areas with ancient volcanic activity like Brazil, India, and the Midwestern United States.

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