sedimentary
Green Jasper (Banded Jasper)
Silicon Dioxide (SiO2) with impurities
Hardness: 6.5–7 on Mohs scale; Color: Dark olive green with subtle banding; Luster: Dull to waxy; Crystal structure: Microcrystalline/Cryptocrystalline (trigonal); Cleavage: None (conchoidal fracture); Specific gravity: 2.6–2.9
- Hardness
- 6
- Color
- Dark olive green with subtle banding
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5–7 on Mohs scale; Color: Dark olive green with subtle banding; Luster: Dull to waxy; Crystal structure: Microcrystalline/Cryptocrystalline (trigonal); Cleavage: None (conchoidal fracture); Specific gravity: 2.6–2.9
Formation & geological history
Formed via the accumulation of silica-rich fluids in volcanic or sedimentary cavities, often during the Proterozoic or Paleozoic eras. The green color is typically attributed to iron silicate minerals like chlorite.
Uses & applications
Used primarily in lapidary work for cabochons, beads, and polished palm stones. Also utilized in construction as aggregate or decorative landscaping stone when found in bulk.
Geological facts
Green jasper was highly prized in the ancient world; it was known as the 'rain bringer' and was frequently mentioned in historical texts as a stone of protection. The banding is caused by variations in mineral concentration during the deposition of the silica layers.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its characteristic smooth, river-tumbled texture. Commonly found in riverbeds and coastal regions of the Pacific Northwest, Madagascar, and India. Collectors look for unique swirling patterns or intense color saturation.
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