sedimentary

Red Jasper

Microcrystalline Quartz (SiO2 with Iron Oxide impurities)

Hardness: 6.5-7 on Mohs scale; Color: Rusty red to brownish-red; Luster: Dull to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.91

Hardness: 6
Color: Rusty red to brownish-red
Luster: Dull to waxy

Identified June 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when fine silica-rich materials are deposited in various environments, such as volcanic ash beds or deep-sea sediments. The red color is caused by the inclusion of iron oxides (hematite) during the silicification process. Common in the sedimentary basins of East-Central Texas.

Uses & applications

Commonly used for lapidary work, jewelry (cabochons, beads), decorative stone in landscaping, and as a popular specimen for rock tumbling and collecting.

Geological facts

Jasper has been used throughout history as a gemstone; it is mentioned in ancient texts and was used for seals and amulets in Mesopotamia and Egypt. It is a variety of chalcedony that is virtually opaque.

Field identification & locations

Identified in the field by its deep red color, hardness (it will scratch glass but cannot be scratched by a steel knife), and smooth, waxy feel when water-worn. Common in river gravels and Eocene-age formations in the Texas Gulf Coastal Plain.

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Sandstone or Siltstone

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Cone-in-cone structure (Limestone)

Cone-in-cone structure (Secondary Sedimentary Structure)

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Chert Breccia

Brecciated Chert (Microcrystalline Silica)

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Sandstone Grain

Clastic Sedimentary Rock Grain (SiO2 dominated)

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Shale or Slaty Mudstone

Argillaceous sedimentary rock

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Sandstone

Arenite (primarily SiO2)

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