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Formula: MgO
Simple oxide, periclase group
Ferropericlase is a Fe(II)-bearing variety of periclase. It is a high-pressure phase, metastable as
inclusions in other minerals Mindat
Crystal System: Isometric
Specific gravity: 3.55 to 3.57 measured, 3.581 calculated
Hardness: 5½
Streak: White
Colour: Colourless, grayish white, yellow, brownish yellow, green, black
Solubility: Insoluble in water, soluble in hydrochloric, nitric and sulphuric acid
Common impurity: Fe
Environments:
Periclase is found as a product of contact metamorphism of
dolomite and
magnesite.
It is a mineral of the amphibolite facies.
Alteration
During the progressive metamorphism of silica-rich dolostones the following approximate sequence of mineral
formation is often found, beginning with the lowest temperature product:
talc,
tremolite,
diopside,
forsterite,
wollastonite,
periclase,
monticellite
brucite to periclase and H2O
Mg(OH)2 ⇌ MgO + H2O
(JVW p102)
The equilibrium temperature for this reaction at 10 kbar pressure is about 840oC
(granulite facies), with the equilibrium to
the right at higher temperatures, and to the left at lower temperatures (for the same pressure)
(SERC).
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