Where is Jasper in Basalt found?
Jasper (SiO2) in Basalt (igneous rock)
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Open the appJasper in Basalt occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Jasper in Basalt
Columbia River Basalt Group, USA
Extensive flood basalts in Washington, Oregon, and Idaho, known for various silica infillings including jasper and agate.
Deccan Traps, India
One of the largest volcanic provinces globally, basalts often contain secondary minerals, including jasper.
Iceland
Active volcanic island with abundant basaltic rocks, where hydrothermal alteration can lead to jasper formation.
Australia
Various basaltic regions, particularly in Western Australia and Queensland, can yield jasper in basalt.
Collecting tips
- Look for Vesicular Basalts. Jasper often forms by filling vesicles (gas bubbles) in basalt. Look for weathered basalt outcrops where these infillings might be exposed.
- Check Fracture Zones. Silica-rich fluids can also precipitate jasper along fractures and faults within basaltic rocks. Examine areas with structural weaknesses.
- Hydrothermal Alteration Zones. Areas showing signs of hydrothermal alteration (e.g., discoloration, presence of other secondary minerals) are good indicators for jasper formation.
- Examine Weathered Surfaces. Weathering can sometimes expose the jasper more clearly by eroding the softer or more fractured basalt matrix.
Quick Check
- Color:
- Dark gray/black basalt with contrasting red, yellow, brown, green, or multicolored opaque inclusions.
- Luster:
- Dull to sub-vitreous basalt, dull to waxy jasper.
- Streak:
- Basalt: Gray to black. Jasper: White.
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