sedimentary
Jasper
Silicon dioxide (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Reddish-brown due to iron inclusions; Luster: Vitreous to waxy; Structure: Microcrystalline quartz; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Reddish-brown due to iron inclusions
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Reddish-brown due to iron inclusions; Luster: Vitreous to waxy; Structure: Microcrystalline quartz; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91
Formation & geological history
Formed from the deposition of silica-rich fluids in volcanic ash or sedimentary deposits, often during the Proterozoic to Cenozoic eras. The red coloring is typically caused by iron (III) oxidation.
Uses & applications
Commonly used in lapidary work, jewelry (cabochons), interior decoration (slabs), and historically used for making stone tools due to its conchoidal fracture.
Geological facts
The name 'Jasper' originates from the Greek word 'iaspis', meaning 'spotted stone.' It has been used for millennia by ancient civilizations, including the Minoans and Egyptians, for seals and amulets.
Field identification & locations
Identify in the field by its opaque nature (unlike translucent chalcedony), smooth conchoidal fracture patterns, and inability to be scratched by a steel knife. Frequently found in riverbeds and gravel deposits worldwide.
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