By Mauro Cateb (Own work) [CC-BY-SA-3.0], via Wikimedia Commons
Pyrite is more commonly known as fool’s gold and is familiar to nearly every mineral collector. It has been used for centuries both in jewelry and as an ore of iron. “Marcasite” stones in jewelry are frequently pyrite, since the latter is more stable. The material is very brittle and heat sensitive and requires some care in cutting. Cabochons are sometimes cut, but they have no special appeal.
| Data | Value |
|---|---|
| Name | Pyrite |
| Colors | Brassy yellow, sometimes with iridescent tarnish. |
| Crystallography | Isometric. Crystals abundant and widespread, sometimes very large and displaying an immense variety of forms; also massive, granular. |
| Luster | Metallic. |
| Hardness | 6-6.5 |
| Fracture | Conchoidal to uneven |
| Specific Gravity | 5.0-5.03 |
| Birefringence | None. |
| Cleavage | Indistinct |
| Stone Sizes | Cabochons of any size could be cut from the large crystals that have been found. Pyrite is usually seen in inexpensive jewelry, faceted in rose—cut fashion with flat backs, similar to the older marcasite jewelry popular during the Victorian era. |
| Transparency | Opaque. |
| Formula |
FeS2. |
| Pleochroism |
None. |
| Optics |
Isotropic. |
Dimorph of Marcasite.
Streak: Greenish black.
Other Tests: Nonmagnetic; insoluble in HCl.
Occurrence: The most abundant of all sulfide minerals; occurs in nearly all rock types and most geological environments. Localities too numerous to list in detail. Fine crystals are known from the following localities:
Leadville, Colorado; French Creek. Pennsylvania;
Bingham, Utah.
Elba, Italy; Ambassaguas, Spain; England; Austria;
Germany; Switzerland; Sweden; Peru; Bolivia.
Comments: Pyrite is more commonly known as fool’s gold and is familiar to nearly every mineral collector. It has been used for centuries both in jewelry and as an ore of iron. “Marcasite” stones in jewelry are frequently pyrite, since the latter is more stable. The material is very brittle and heat sensitive and requires some care in cutting. Cabochons are sometimes cut, but they have no special appeal.
Name: From the Greek word for fire, because pyrite emits sparks when struck like a flint.
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