Sedimentary / Metamorphic

Jasper (Iron-rich Chalcedony)

Jasper (Microcrystalline Silicon Dioxide, SiO2 plus iron oxide impurities)

Hardness: 6.5-7 (Mohs scale); Color: Dark reddish-brown to maroon; Luster: Dull to waxy; Crystal structure: Hexagonal (cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.91.

Hardness: 6
Color: Dark reddish-brown to maroon
Luster: Dull to waxy

Identified March 29, 2026More sedimentary / metamorphic →

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Physical properties

Formation & geological history

Formed from the deposition of silica from volcanic ash flows or hot springs into sedimentary environments. Its reddish color is due to the oxidation of iron within the silica matrix during its formation, often dating back to the Paleozoic or Mesozoic eras.

Uses & applications

Commonly used for lapidary work, jewelry (cabochons), interior ornaments, and as a durable material in construction and landscaping. It is also a popular collectible for 'rockhounding'.

Geological facts

Jasper has been used as a gemstone since antiquity and is mentioned in the Bible. It is a variety of chalcedony that is made opaque by its high mineral impurity content (up to 20%).

Field identification & locations

Identify in the field by its opacity (even on thin edges), smooth river-worn texture, and inability to be scratched by a steel knife. It is commonly found in riverbeds, glacial tills, and coastal beaches.

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Dalmatian Stone

Dalmatian Jasper (a misnomer) / Perthitic Igneous Rock

igneous

Anthracite Coal

Anthracite (Carbon-based sedimentary-metamorphic rock)

metamorphic

Anthracite Coal

Anthracite (Carbon-based organic sedimentary/metamorphic rock)

metamorphic

Coal (Anthracite)

Anthracite (Carbon-based organic sedimentary/metamorphic rock)

metamorphic

Quartz Vein in Host Rock

Silicon Dioxide (SiO2) within Sedimentary/Metamorphic Matrix

Metamorphic or Igneous (context dependent)

Sandstone, Quartzite, and River Pebbles

Silicon Dioxide (SiO2) based Sedimentary/Metamorphic structures

Sedimentary and Metamorphic