sedimentary
Jasper (Chert)
Silicon Dioxide (SiO2) with iron oxide inclusions
Hardness: 6.5-7 (Mohs scale), Color: Yellow-brown (ochre) with reddish veins, Luster: Dull to waxy (smooth when wet), Structure: Microcrystalline/Cryptocrystalline, Cleavage: None (conchoidal fracture)
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Yellow-brown (ochre) with reddish veins, Luster: Dull to waxy (smooth when wet), Structure: Microcrystalline/Cryptocrystalline, Cleavage: None (conchoidal fracture)
Formation & geological history
Formed primarily through the accumulation of silica-rich fluids in volcanic or sedimentary environments, often associated with iron impurities that lend it the yellowish-brown hue. These water-worn pebbles are typically found in riverbeds or coastal areas.
Uses & applications
Used frequently in lapidary work for cabochons, beads, and decorative ornaments. Also sought after by rockhounds and collectors for its aesthetic patterns.
Geological facts
Jasper is an opaque variety of chalcedony. The yellow and brown colors in this specimen are typically caused by goethite or limonite (iron oxides). Historically, jasper was used to make tools due to its conchoidal fracturing.
Field identification & locations
Identify in the field by its hardness (it will scratch glass), its opaquer nature compared to agate, and its smooth, water-worn texture. Commonly found in gravel pits, beaches, and riverbanks globally.
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