Where is Pyrite in fine-grained mafic or ultramafic rock found?
Pyrite (FeS2) in a fine-grained mafic or ultramafic rock
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Open the appPyrite in fine-grained mafic or ultramafic rock 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 Pyrite in fine-grained mafic or ultramafic rock
Sudbury Basin, Ontario, Canada
Known for its large nickel-copper sulfide deposits, where pyrite is a common accessory mineral within mafic-ultramafic intrusions and breccias.
Bushveld Complex, South Africa
A vast layered mafic-ultramafic intrusion where pyrite can be found associated with platinum-group element (PGE) and chromite mineralization.
Cyprus Ophiolite, Cyprus
Classic example of an ophiolite complex, where massive sulfide deposits (including pyrite) are hosted within mafic volcanic rocks (pillow basalts) and associated with hydrothermal activity.
Norilsk-Talnakh, Siberia, Russia
World-class nickel-copper-PGE deposits hosted in mafic-ultramafic intrusions, with significant pyrite mineralization.
Various greenstone belts worldwide
Ancient volcanic-sedimentary terrains (e.g., Yilgarn Craton, Australia; Abitibi Greenstone Belt, Canada) often contain mafic volcanic rocks with associated gold and base metal deposits where pyrite is abundant.
Collecting tips
- Look for metallic luster. Pyrite's distinct brassy yellow metallic luster will stand out against the darker, duller matrix of the mafic or ultramafic host rock.
- Examine fresh breaks. Weathered surfaces of pyrite can be tarnished or oxidized. Look for freshly broken surfaces to observe the true color and luster.
- Check for crystal forms. Search for cubic, pyritohedral, or octahedral crystal shapes, which are characteristic of pyrite, especially in vugs or along fracture surfaces.
- Consider geological context. Pyrite is often associated with hydrothermal alteration zones, shear zones, or contact metamorphic aureoles within mafic/ultramafic bodies. Look for evidence of these processes.
- Perform a streak test. Pyrite leaves a greenish-black streak, which helps distinguish it from gold (yellow streak) and chalcopyrite (greenish-black streak, but with a more yellowish hue).
- Test for hardness. Pyrite is relatively hard (6-6.5 on Mohs scale), which means it will scratch glass and will not be easily scratched by a steel knife.
Quick Check
- Color:
- Brassy yellow (pyrite) in dark gray/green/black (host rock)
- Luster:
- Metallic (pyrite) in dull to sub-vitreous (host rock)
- Streak:
- Greenish-black (pyrite)
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