
“Magnesium Oxide (Periclase),” synthetic, doped with nickel, ~ 5 carats. Photo © Joel E. Arem, PhD, FGA. Used with permission.
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.
Optics: Isotropic; N: 1.736.
Occurrence: Occurs in marbles, due to high-temperature contact metamorphism.
Texas; New Mexico.
Spain; Sardinia; Czech Republic; Slovakia.
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.