Siderite
Siderite is a rare and beautiful gem that is difficult to facet due to its perfect rhombohedral cleavages and brittleness. It is a category of Carbonate mineral and the formula of Siderite is FeCO3(iron(II)carbonate). It is in the color of Yellowish Brown, Brown, Gray, Yellowish Gray, Greenish Gray. When coming to its Crystal habit it has Commonly crystallized, typically rhombohedral [1011] to steep scalenohedral [2131], prismatic [1010], [0001], with additional minor forms, to 25 cm; fibrous, stalactitic, spherulitic, cleavable, fine-grained massive. It is in a mineral series with Rhodchrosite (MnCO3) and Calcite (CaCO3). It is found at several locations around the world, but gem quality crystals are somewhat rare. The Cleavage of this stone is perfect on [1011] and the hardness of this gem is between 3.75 – 4.25. The main sources are Mont Sainte Hilaire, Quebec, Canada (brown) and Panesqueria, Portugal (green).
| Category: | Carbonate mineral |
| Formula: | FeCO3 |
| iron(II) carbonate | |
| Crystallography: | Trigonal – Hexagonal – Scalenohedral |
| Crystal Habit: | Commonly crystallized, typically rhombohedral [1011] to steep scalenohedral [2131], prismatic [1010], [0001], with additional minor forms, to 25 cm; fibrous, stalactitic, spherulitic, cleavable, fine-grained massive. |
| Twinning: | Uncommon on [0112], lamellar; rare on [0001] |
| Cleavage: | [1011] Perfect, [1011] Perfect, [1011] Perfect |
| Fracture: | Conchoidal, Irregular/Uneven |
| Tenacity: | Very Brittle |
| Hardness (Mohs): | 3.75 – 4.25 |
| Density: | 3.96 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioacitve |
| Other: | Slightly soluble in water. |
| Color: | Yellowish Brown, Brown, Gray, Yellowish Gray, Greenish Gray |
| Transparency: | Transparent, Translucent |
| Luster: | Vitreous, Pearly, Silky |
| Refractive Index: | 1.633 – 1.875 Uniaxial ( – ) |
| Birefringence: | 0.215 – 0.242 (very high) |
| Dispersion: | Strong |
| Pleochroism: | None |
