Jasper-Quartz Conglomerate / Chert

Physical Properties

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, tan, and white translucent patches; Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: ~2.65

Formation & Geological History

Formed through the accumulation of silica-rich sediments or the chemical replacement of existing limestone/carbonate rocks by silica-rich fluids. Often found as water-worn river pebbles or in glacial till.

Uses & Applications

Used primarily for lapidary work (cabochons, tumbling), decorative landscaping, and as a collector's specimen. Historically used for tool-making due to its durability.

Geological Facts

This specimen appears to be a 'puddingstone-like' conglomerate or a brecciated jasper. The red color usually indicates the presence of iron oxide (hematite) staining the silica structure.

Field Identification & Locations

Identify in the field by its hardness (it will scratch glass), its smooth water-worn texture, and the presence of mixed colors (white quartz clasts in a red ferruginous matrix). Common in riverbeds and Great Lakes shorelines.

Identified on: 4/21/2026

Mode: Standard