sedimentary
Jasper
Silicon Dioxide (SiO2) with iron oxide impurities
Hardness: 6.5-7 (Mohs scale); Color: Reddish-brown, earthy; Luster: Glossy to dull/waxy; Crystal Structure: Microcrystalline (trigonal); Cleavage: None/Conchoidal fracture.
- Hardness
- 6
- Color
- Reddish-brown, earthy
- Luster
- Glossy to dull/waxy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Reddish-brown, earthy; Luster: Glossy to dull/waxy; Crystal Structure: Microcrystalline (trigonal); Cleavage: None/Conchoidal fracture.
Formation & geological history
Formed from silica-rich fluids and volcanic ash deposits that permeate porous rocks or replace organic matter over millions of years, often occurring in volcanic or sedimentary environments.
Uses & applications
Used primarily in lapidary arts for jewelry, beads, and cabochons. Historically used for making stone tools and ornaments.
Geological facts
Jasper is an opaque variety of chalcedony. The red color is typically caused by inclusions of hematite (iron oxide). It has been a popular gemstone since ancient times and is mentioned in various historical and religious texts.
Field identification & locations
Identify in the field by its hardness (will scratch glass), opaque nature, and smooth, curved (conchoidal) fracture surfaces. Commonly found in riverbeds and desert environments such as the American Southwest and India.
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