Agate

Physical Properties

Hardness: 6.5-7 Mohs; Color: Translucent pink, tan, with white banding; Luster: Waxy to vitreous; Crystal Structure: Trigonal (cryptocrystalline quartz); Cleavage: None; Specific Gravity: 2.58-2.64

Formation & Geological History

Formed in cavities of volcanic rocks or ancient lavas through the deposition of silica-rich groundwater. Over time, layers of microcrystalline quartz build up to create the characteristic banding. Found in formations ranging from 50 million to 1 billion years old.

Uses & Applications

Used in gemstone carvings, jewelry, ornamental objects, and industrial precision instruments like mortar and pestles due to its hardness and resistance to acids.

Geological Facts

Agate is uniquely identifiable by its banding patterns. The pink variety often gains its hue from trace amounts of manganese or iron. It has been used in amulets since the time of Ancient Egypt.

Field Identification & Locations

Identify in the field by looking for a waxy luster on fractured surfaces and concentric or parallel banding. Commonly found in riverbeds, desert surfaces, and volcanic regions globally (notably Brazil, Uruguay, and USA).

Identified on: 5/10/2026

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