Marcasite
| Formula | FeS2 |
| Origin | Jerusalem, Pribram (Czech Republic) |
| Description | Marcasite in the form of Speerkies. |
| Classification (Lapis) | Sulfides |
| Crystal System | orthorhombic |
| Hardness | 6,0 – 6,5 |
| Colour | Tin-white on fresh surface, pale bronze-yellow, darkening on exposure, iridescent tarnish |
| Streak | Grayish or brownish black |
| Luminescence | none observed |
| Lustre | metallic |
| Transparency (Opacity) | opaque |
| Cleavage | distinct |
| Fracture | splintery |
| Magnetism | negative |
| Geological Setting | typically formed under low-temperature highly acidic conditions, both in sedimentary environments (shales, limestones, and low rank coals) and in hydrothermal veins formed by ascending solutions |
| Specific Gravity | 4,8 g/cm3 |
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#© Mark Holtkamp
