Rock Identifier
Banded Agate (Cryptocrystalline Quartz (SiO2)) — mineral
mineral

Banded Agate

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 Mohs; Color: Tan, brown, and translucent orange bands; Luster: Vitreous to waxy (when polished); Structure: Hexagonal (microcrystalline); Cleavage: None; Conchoidal fracture.

Hardness
6
Color
Tan, brown, and translucent orange bands
Luster
Vitreous to waxy (when polished)
Identified More mineral
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Physical properties

Hardness: 6.5-7 Mohs; Color: Tan, brown, and translucent orange bands; Luster: Vitreous to waxy (when polished); Structure: Hexagonal (microcrystalline); Cleavage: None; Conchoidal fracture.

Formation & geological history

Formed primary in volcanic rock cavities (vesicles) where silica-rich groundwater deposits layers over time, creating distinctive banding patterns. Found in rocks ranging from millions to billions of years old.

Uses & applications

Used extensively in jewelry as cabochons, decorative carvings, metaphysical 'healing' stones, and historically for precision bearings and mortars.

Geological facts

The name 'Agate' comes from the Achates River in Sicily where these stones were first found in ancient times. Every agate is unique due to the specific mineral impurities during formation.

Field identification & locations

Identify in the field by looking for waxy luster, translucency when held to light, and concentric banding. Commonly found in gravel beds, lake shores (like Lake Superior), and volcanic outcrops.