Periclase
Periclase is a very rare magnesium oxide mineral that is rarely available as a faceted gem. The chemical formula of Periclase is MgO (Magnesium Oxide) and its molecular weight is 40.30 gm. It is usually found as a component of metamorphosed dolomitic limestones and readily alters to Brucite and other magnesium minerals under certain conditions. Periclase has a specific gravity of 3.56 – 3.68 (g/cm3) and Refractive index of 1.735 – 1.745 Isotropic. Moh’s Hardness of 5.5. Periclase has been synthesized in large masses in the laboratory, but faceted natural Periclase would is very rare due to the extreme scarcity of facetable rough.
There are a number of locations for finding Periclase but facet grade crystals may only be available from the Ronneburg U deposit, Gera, Thuringia, or the Lichtenberg Absetzer Mine (dump), Ronneburg U deposit, Gera, Thuringia, Germany.
| Catagory: | Oxide minerals | |||||||||||||||
| Chemical Formula: | MgO | |||||||||||||||
| Magnesium Oxide | ||||||||||||||||
| Molecular Weight: | 40.30 gm | |||||||||||||||
| Composition: |
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| Crystallography: | Isometric – Hexoctahedral |
| Crystal Habit: | As small octahedra, less commonly cubo-octahedra or dodecahedra, may be clustered; granular, massive. |
| Twinning: | None |
| Cleavage: | [001] Perfect, [111] Imperfect; may exhibit parting on [011] |
| Fracture: | Irregular/Uneven, Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 5.5 |
| Density: | 3.56 – 3.68 (g/cm3) |
| Luminescence: | Light Yellow under LW UV |
| Radioactivity: | Not Radioactive |
| Other: | Slightly soluble in water when powdered, to give an alkaline reaction |
| Color: | Colorless, Grayish White, Yellow, Brownish Yellow; maybe Green or Black with inclusions; Colorless in transmitted light. |
| Transparency: | Transparent to Translucent |
| Luster: | Vitreous |
| Refractive Index: | 1.735 – 1.745 Isotropic |
| Birefringence: | 0.00 (Isotropic) |
| Dispersion: | Relatively Strong |
| Pleochroism: | None |
