Chalcedony (Blue/Grey Lace Agate)

Physical Properties

Hardness: 6.5-7 on Mohs scale. Color: Pale blue, lavender, or grey with subtle banding. Luster: Waxy to vitreous. Crystal Structure: Trigonal (cryptocrystalline). Cleavage: None. Specific Gravity: 2.58-2.64.

Formation & Geological History

Formed from the deposition of silica-rich water in cavities (vugs) within volcanic and sedimentary rocks. Typically formed during Cenozoic eras in secondary hydrothermal environments.

Uses & Applications

Commonly used in jewelry for cabochons and beads, as well as for decorative carvings, orbital polishers, and spiritual or metaphysical collecting.

Geological Facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are so small they can only be seen with extreme magnification. It has been used since the Bronze Age for seals and cylinder stamps.

Field Identification & Locations

Identify by its waxy luster, lack of cleavage, and translucent edges. It is often found in riverbeds or volcanic outcrops. Major deposits are found in Namibia, Brazil, and the USA (South Dakota and Oregon).

Identified on: 4/28/2026

Mode: Standard