mineral

Banded Agate with Druzy Quartz

Agate (Silicon Dioxide - SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Blue-grey, white, and translucent; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal (cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.58–2.64.

Hardness: 6
Color: Blue-grey, white, and translucent
Luster: Vitreous to waxy

Identified March 27, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica from groundwater into cavities (vesicles) within igneous volcanic rocks such as basalt or rhyolite. The distinct banding represents different cycles of mineral precipitation. Specimens like this often date from the Cenozoic or Mesozoic eras.

Uses & applications

Commonly used for ornamental purposes, lapidary carvings (like this polished tower/point), jewelry, and by collectors. In industry, due to its hardness and resistance to chemicals, it is used for making precision mortars and pestles.

Geological facts

The banding in agate is caused by the rhythmic precipitation of silica over long periods. This specific specimen features a 'druzy' pocket, which is a cavity lined with small, sparkling macroscopic quartz crystals that did not fully fill the void during formation.

Field identification & locations

Identify in the field by its waxy luster, distinct concentric or planar banding, and its ability to scratch glass. It is commonly found in Brazil, Uruguay, and the United States (specifically the Lake Superior region and Oregon). Collectors look for clarity and high-contrast banding.

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