sedimentary

Jasper

Silicon Dioxide (SiO2) with iron oxide impurities

Hardness: 6.5-7 (Mohs scale), Color: Reddish-brown, Luster: Dull to Vitreous (when polished), Crystal Structure: Trigonal (microcrystalline/cryptocrystalline), Cleavage: None, Specific Gravity: 2.58-2.91

Hardness: 6

Identified July 6, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the deposition of silica from water or hydrothermal vents, often in sedimentary environments where iron oxides and other impurities are present to provide the red coloration. Commonly found in ancient sea beds.

Uses & applications

Primarily used as a gemstone for jewelry, cabochons, decorative carvings, and as a collector specimen. Historically used for making tools and seals due to its hardness and lack of cleavage.

Geological facts

The name Jasper comes from the Greek word 'iaspis', meaning 'spotted stone'. In ancient times, it was believed to ward off evil spirits and protect the wearer from scorpion stings. It is a variety of chalcedony that is opaque due to high mineral impurity content.

Field identification & locations

Identify in the field by its opaque nature (unlike agate), smooth conchoidal fracture, and hardness (it will scratch glass). It is frequently found as well-rounded pebbles in riverbeds or beaches where water has smoothed the rough stone over time.

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Sandstone or Siltstone

Arenite (if sandstone)

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Cone-in-cone structure (Limestone)

Cone-in-cone structure (Secondary Sedimentary Structure)

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Sandstone Grain

Clastic Sedimentary Rock Grain (SiO2 dominated)

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Chert Breccia

Brecciated Chert (Microcrystalline Silica)

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Shale or Slaty Mudstone

Argillaceous sedimentary rock

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Sandstone

Arenite (primarily SiO2)

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