sedimentary
Jasper
Silicon Dioxide (SiO2) with iron oxide inclusions
Hardness: 6.5-7 (Mohs scale); Color: Brick red to brownish-red with dark crust; Luster: Vitreous to waxy; Structure: Cryptocrystalline (microscopic crystals); Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Brick red to brownish-red with dark crust
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Brick red to brownish-red with dark crust; Luster: Vitreous to waxy; Structure: Cryptocrystalline (microscopic crystals); Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from the deposition of silica from water (often hydrothermal or volcanic) into cracks or cavities. Over time, the silica crystallizes with impurities, such as hematite, which provide the red color. These can date back from millions to billions of years depending on the host rock.
Uses & applications
Commonly used as a gemstone for cabochons in jewelry, pocket stones for decorative collecting, and occasionally in larger slabs for ornamental masonry or crafts.
Geological facts
Jasper is an opaque variety of chalcedony. Historically, it was known as the 'supreme nurturer' in ancient cultures and has been used for seals and amulets since the Minoan era.
Field identification & locations
Identify in the field by its conchoidal (shell-like) fracture patterns and inability to be scratched by a steel nail. It is often found in riverbeds, desert washes, and areas with ancient volcanic activity.
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