mineral

Agate

Silicon dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Multi-colored (yellow, orange, white/translucent); Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None; SG: 2.58-2.64

Hardness: 6
Color: Multi-colored (yellow, orange, white/translucent)
Luster: Waxy to vitreous

Identified May 9, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Multi-colored (yellow, orange, white/translucent); Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None; SG: 2.58-2.64

Formation & geological history

Formed as a secondary mineral in volcanic rock cavities (vesicles) or sedimentary formations through the deposition of silica from groundwater. This specific piece appears to be a water-worn river pebble.

Uses & applications

Used primarily for jewelry (cabochons), interior decor, burnishing tools, and as a popular collector's gemstone due to its durability and aesthetics.

Geological facts

Agate is a variety of chalcedony. The name comes from the Achates River in Sicily where they were found in ancient times. It is the birthstone for September and the mystical birthstone for Gemini.

Field identification & locations

Identify by its hardness (cannot be scratched by a steel knife) and its translucent patches. Commonly found in riverbeds, lake shores (like Lake Superior), and volcanic regions. Collectors look for unique banding or 'fortification' patterns.