sedimentary
Coffee Bean Jasper
Silicon Dioxide (SiO2) with impurities
Hardness: 6.5-7 (Mohs scale), Color: Brown, tan, and cream mottled patterns, Luster: Vitreous to dull (waxy when polished), Crystal Structure: Trigonal (microcrystalline/cryptocrystalline), Cleavage: None, Specific Gravity: 2.58-2.91
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Brown, tan, and cream mottled patterns, Luster: Vitreous to dull (waxy when polished), Crystal Structure: Trigonal (microcrystalline/cryptocrystalline), Cleavage: None, Specific Gravity: 2.58-2.91
Formation & geological history
Formed through the infiltration of silica in sedimentary rocks or volcanic ash, combined with iron oxides and other mineral impurities that create the dendritic or mottled patterns. Often found in South Africa and North America.
Uses & applications
Primarily used for lapidary work, jewelry (beads, cabochons), home decor, and as a pocket stone for collectors.
Geological facts
The name 'Jasper' is derived from the Greek word 'iaspis', meaning spotted stone. It is a variety of chalcedony that is opaque due to its high mineral content.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a steel knife) and its smooth, opaque, earthy appearance. Look for it in regions with high volcanic activity or ancient sedimentary basins.
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