Banded Agate (Carnelian type)

Physical Properties

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, orange, and tan banding; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.64

Formation & Geological History

Formed by the deposition of silica from groundwater in the cavities of igneous rocks such as basalt or rhyolite. The banding results from rhythmic crystallization and varied mineral impurities like iron oxides during formation.

Uses & Applications

Used primarily in jewelry (cabochons, beads), decorative carvings, lapidary arts, and as a collector's specimen. Historically used for making seals and amulets.

Geological Facts

Agate was named by Theophrastus, a Greek philosopher, who discovered the stone along the Achates River in Sicily. Carnelian-variety agates have been used for decorative purposes for over 4,000 years.

Field Identification & Locations

Identify in the field by its waxy luster, hardness (it will scratch glass), and distinctive concentric or parallel banding when held to a light source. Commonly found in riverbeds, volcanic ash deposits, and along beaches in regions like Brazil, India, and the Lake Superior region of the USA.

Identified on: 4/13/2026

Mode: Standard