sedimentary

Jasper (Iron-stained Chert)

Silicon Dioxide (SiO2) with impurities of Hematite or Goethite

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, mustard yellow, and tan; Luster: Dull to waxy; Crystal Structure: Microcrystalline (Cryptocrystalline) trigonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9.

Hardness: 6
Color: Reddish-brown, mustard yellow, and tan
Luster: Dull to waxy

Identified March 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the precipitation of silica from circulating hydrothermal fluids or by the deposition of silica-rich organic remains (like radiolaria) which crystallize over millions of years. This specific specimen shows water-worn rounding, suggesting a fluvial (river) or glacial transport history.

Uses & applications

Commonly used in lapidary work for cabochons, beads, and tumbled stones. Historically used for making stone tools (scrapers, arrowheads) due to its conchoidal fracture and hardness.

Geological facts

Jasper is an opaque variety of chalcedony. The brown and yellow colors in this specimen are caused by the oxidation of iron minerals (limonite or hematite) within the silica matrix.

Field identification & locations

Identify in the field by its hardness (will scratch glass), opaque nature (unlike translucent agate), and smooth, water-worn exterior if found in gravel pits or riverbeds. Common in glacial drift across North America.

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