sedimentary

Red Jasper (River Siltstone)

Silicon Dioxide (SiO2) with iron oxide inclusions

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown to brick red; Luster: Waxy to vitreous when polished; Crystal structure: Hexagonal (microcrystalline/cryptocrystalline); Cleavage: None; Specific gravity: 2.58-2.91

Hardness: 6
Color: Reddish-brown to brick red
Luster: Waxy to vitreous when polished

Identified April 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from microcrystalline quartz and chalcedony with iron impurities. This specific smooth, rounded specimen originated through fluvial (river) erosion, where water action tumbled the stone over a long period, typically originating from Mesozoic or Paleozoic sedimentary layers.

Uses & applications

Commonly used in lapidary work for cabochons, beads, and decorative carvings. Industrially used as abrasive material in some contexts, or as aggregate in high-end landscaping.

Geological facts

Jasper was a favorite gem in the ancient world, referenced in many historical texts and found in Minoan seals from 1800 BC. The red color is almost exclusively caused by the presence of iron (hematite).

Field identification & locations

Identify in the field by its opaque nature (unlike translucent carnelian), its high hardness (it will scratch glass), and its smooth water-worn texture if found near rivers. Common in Western US (Oregon, Idaho) and India.

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