“Magnesium Oxide (Periclase),” synthetic, doped with nickel, ~ 5 carats
Periclase has been synthesized in large masses in the laboratory, but these have no market significance. A faceted natural periclase would be a great rarity due to the extreme scarcity of suitable faceting rough. The expected size would be less than 1 carat.
Periclase Value
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Periclase Information
| Data | Value |
| Name | Periclase |
| Crystallography | Isometric. Crystals octahedral, cubic; commonly as rounded grains. |
| Colors | Colorless, white, gray, yellow, brownish yellow, green, black. |
| Luster | Vitreous. |
| Hardness | 5.5. |
| Density | 3.56. |
| Cleavage | Perfect 1 direction. Fracture uneven. Brittle. |
| Stone Sizes | I have not seen any faceted gems, but if such gems existed, they would be very small. Transparent grains from Vesuvius might be cuttable, but in general periclase is not known in transparent. large crystals. |
| Luminescence | Pale yellow in LW (Terlingua, Texas). |
| Formula | MgO |
Optics: Isotropic; N: 1.736.
Occurrence: Occurs in marbles, due to high-temperature contact metamorphism.
Texas; New Mexico.
Spain; Sardinia; Czechoslovakia.
Crestmore, Riverside County, California: embedded grains.
Vesuvius, Italy: as glassy grains in the lava rocks.
Nordmark, Sweden: in the Mn mines.
Comments: Periclase has been synthesized in large masses in the laboratory, but these have no market significance. A faceted natural periclase would be a great rarity due to the extreme scarcity of suitable faceting rough. The expected size would be less than 1 carat.
Name: From the Greek peri plus klastos, to break around, in allusion to the cleavage.
