Where is Pyrite in host rock found?
Pyrite (FeS2) in sedimentary or metamorphic rock
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Open the appPyrite in host 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 host rock
Rio Tinto, Spain
Famous for massive sulfide deposits, including pyrite, hosted in volcanic and sedimentary rocks.
Navajún, La Rioja, Spain
Renowned for producing world-class, perfectly formed cubic pyrite crystals in marl (a type of sedimentary rock).
Illinois, USA
Known for pyrite concretions and nodules in coal seams and shales.
Peruvian Andes
Numerous polymetallic deposits contain significant pyrite in various host rocks, often associated with other sulfides.
Various gold districts worldwide
Pyrite is a common accessory mineral in many gold deposits (e.g., Witwatersrand Basin, South Africa; Carlin Trend, USA), where gold can be 'refractory' within the pyrite lattice.
Collecting tips
- Look for metallic luster. Pyrite's bright, metallic sheen is often the first indicator. Even small specks can catch the light.
- Check for brassy color. The characteristic pale brass-yellow color helps distinguish it from other minerals. Be aware of tarnishing which can make it appear darker or iridescent.
- Observe crystal habit. Look for cubic, pyritohedral, or octahedral forms, especially in vugs or open spaces within the host rock. Striations on cube faces are a good diagnostic feature.
- Test streak. A greenish-black to brownish-black streak is diagnostic for pyrite, differentiating it from gold (yellow streak) and chalcopyrite (greenish-black streak).
- Consider geological context. In sedimentary rocks, look in black shales, coal seams, and areas with abundant organic matter. In metamorphic terrains, check for hydrothermal alteration zones or sulfide-rich layers.
- Be aware of weathering. Pyrite weathers readily in oxygenated environments, forming iron oxides (limonite, goethite) and sulfuric acid. This can create rusty stains on the host rock or vugs where pyrite once was.
Quick Check
- Color:
- Brassy yellow
- Luster:
- Metallic
- Streak:
- Greenish-black to brownish-black
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