mineral

Agate

Chalcedony (Cryptocrystalline variety of Quartz, SiO2)

Hardness: 6.5-7 Mohs; Color: Brown, tan, reddish, and translucent white with visible banding; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.58–2.64.

Hardness: 6
Luster: Waxy to vitreous

Identified June 28, 2026More mineral →

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Physical properties

Formation & geological history

Formed primary in volcanic or metamorphic rocks when silica-rich groundwater fills cavities (vugs or bubbles). This specimen shows a rough exterior with typical botryoidal and banded interior formations.

Uses & applications

Commonly used for gemstones, jewelry, lapidary carvings, precision pendulums, and industrial use in mortars and pestles due to hardness.

Geological facts

Agate was names by Theophrastus, a Greek philosopher, who discovered the stone along the shore of the river Achates in modern-day Sicily. It is one of the most common materials used in the art of hardstone carving.

Field identification & locations

Identify in the field by looking for a waxy luster, conchoidal fracture (curved breaks), and subtle banding or translucency when held to light. Often found in dry riverbeds or near volcanic outcrops.

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Mineral

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Mineral/Rock

Banded Gneiss (River Rock/Pebble)

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