Arsenopyrite
| Synonyms: | Arsenical Iron, Arsenical Pyrites, Arsenomarcasite, Dalarnite, Plinian, Thalheimite |
| Classification: | Sulfides, Arsenopyrite Group |
| Chemical formula: | FeAsS |
| Crystal system: | Monoclinic |
| Density (g/cm3): | 6,07 Measured - 6,18 Calculated |
| Tenacity: | Brittle |
| Cleavage: | Distinct/good, distinct on {001}; {010} in traces |
| Fracture: | Irregular/Uneven |
| Hardness (Mohs): | 5,5 - 6 |
| Colour: | Silver-white to steel-gray, may have a slight yellow appearance |
| Lustre: | Metallic, Sub-Metallic |
| Streak: | Gray-black |
| Application: | The most important arsenic ore |