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Periclase
Current inventory:  0 gems
 

  
Periclase is named from the Greek words "peri" and "klastos" meaning "to break around", in allusion to the perfect cubic cleavage.

Discovered in 1840;   IMA status: Valid (pre-IMA; Grandfathered).

Chemistry

Chemical Formula:

MgO

Magnesium Oxide

Molecular Weight:

40.30 gm

Composition: 

Classification

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/A.04-10

Nickel-Strunz 10th Ed. ID:

4.AB.25

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
A : Metal: Oxygen = 2:1 and 1:1
B : M:O = 1:1 (and up to 1:1.25); with small to medium-sized cations only

Related to:

Periclase Group. Periclase - Murdochite Series. Isostructural with Halite.

Varieties:

Ferropericlase, Lavernite

Synonyms:

Periclasa, Periclasia, Periclasite

Crystal Data

Crystallography:

Isometric - Hexoctahedral

Crystal Habit:

As small octahedra, less commonly cubo-octahedra or dodecahedra, may be clustered; granular, massive.

Twinning:

None

Physical Properties

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

Optical Properties

Color:

Colorless, Grayish White, Yellow, Brownish Yellow; may be 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

Occurances

Geological Setting:

A product of the high-temperature metamorphism of magnesian limestones and dolostone.

Common Associations:

Forsterite, Magnesite (Monte Somma, Italy); Brucite, Ellestadite, Hydromagnesite (Crestmore quarry, California, USA); Anhydrite, Fluorellestadite, Hematite, Lime, Magnesioferrite, Srebrodolskite, (Kopeysk, Russia).

Common Impurities:

Fe

Type Locality:

Monte Somma, Somma-Vesuvius Complex, Naples Province, Campania, Italy

Year Discovered:

1840

View mineral photos:

Periclase Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Periclase is a very rare magnesium oxide mineral that is rarely available as a faceted gem. 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 been synthesized in large masses in the laboratory, but faceted natural Periclase would is very rare due to 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.
 

  
Periclase gems for sale:

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