Banded Agate / Lace Agate

Physical Properties

Hardness: 6.5–7 (Mohs scale); Color: White, brown, tan, gray; Luster: Waxy to vitreous; Crystal Structure: Trigonal (cryptocrystalline chalcedony); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.64.

Formation & Geological History

Formed in cavities (vugs) within volcanic rock or ancient hydrothermal veins. Agate develops as silica-rich groundwater precipitates in layers over millions of years. This piece specifically shows a rhythmic banding pattern typical of secondary silica deposition.

Uses & Applications

Used primarily in lapidary arts, jewelry (cabochons), interior decor, and as a semi-precious gemstone for collectors. Historically used for making mortars and pestles due to its hardness.

Geological Facts

Agate is a variety of chalcedony. The name comes from the Achates River in Sicily where agates were first discovered. The banding is often caused by minuscule variations in iron or manganese impurities during the cooling and crystallization process.

Field Identification & Locations

Identify in the field by its distinctive parallel color bands and translucent edges when held to light. It is commonly found in riverbeds or weathered volcanic ash deposits. It won't be scratched by a steel knife.

Identified on: 4/25/2026

Mode: Standard