Jasper (likely Lake Superior Jasper)

Physical Properties

Hardness: 6.5–7 (Mohs scale); Color: Red, brown, and yellow hues with grey zones; Luster: Dull to waxy; Crystal Structure: Microcrystalline/Cryptocrystalline (hexagonal/trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6–2.9

Formation & Geological History

Formed from silica-rich hydrothermal fluids or within sedimentary layers where iron oxides provide coloration. These specific river-worn pebbles often originate from Precambrian-aged formations (over 1 billion years old) and were transported by glacial activity.

Uses & Applications

Used primarily in lapidary arts for making cabochons and tumbled stones, as a decorative pebble in landscaping, and as a popular specimen for amateur rock hounds.

Geological Facts

Jasper is an opaque variety of chalcedony. The red coloration is typically caused by inclusions of hematite (iron oxide). It was used in ancient times to create seals and amulets because of its toughness.

Field Identification & Locations

Identify in the field by its hardness (it will scratch glass) and its smooth, water-worn texture if found near rivers or glacial deposits. Commonly found in the Great Lakes region of North America and along gravel bars.

Identified on: 4/19/2026

Mode: Standard