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Formula: Ca6Zr2(Si2O7)2O4
Sorosilicate (Si2O7 groups),
wöhlerite group,
zirconium-bearing mineral
Crystal System: Monoclinic
Specific gravity: 3.48 calculated
Hardness: 6
Streak: White
Colour: Colourless, pale brown, beige, pale yellowish
Solubility: Slowly soluble in concentrated hydrochloric acid, insoluble in concentrated nitric and sulphuric acids (Dana)
Common impurities: Al,Fe,Mg,Na
Environments
Baghdadite is extremely rare. It occurs in melilite
skarn in contact with banded diorite, in
roof pendant xenoliths of calc-silicate marble and
hornfels (Webmin).
In melilite skarn Baghdadite is associated
with åkermanite, perovskite,
schorlomite, monticellite,
wollastonite, foshagite,
calcite, phlogopite,
spinel, cuspidine,
baddeleyite, pyrrhotite,
djerfisherite and valleriite (HOM).
In banded diorite it is associated with albite variety
andesine,
kaersutite, titanian augite,
ilmenite, titaniferous magnetite and
xonotlite (HOM).
Localities
At the type locality, the Dupezeh mountain, Hero, Qala-Diz, Sulaymaniyah, Iraqi Kurdistan, Iraq, baghdadite has been found in
melilite skarn in contact with banded
diorite, composed chiefly of albite variety andesine
and kaersutite with ubiquitous
titanium-rich augite,
ilmenite and
titaniferous magnetite. The
melilite skarn is cut by randomly distributed
veinlets of foshagite and a few small patches of
monticellite and wollastonite surrounded by
a xonotlite rim. The mineral assemblage of the melilite
skarn was composed of melilite,
perovskite, garnets
(grossular, schorlomite and
Zr-schorlomite), and in addition
monticellite,
wollastonite, titanium-rich augite and
foshagite with accessory phlogopite,
chlorospinel, cuspidine,
baddeleyite, baghdadite, pyrrhotite,
djerfisherite, and valleriite. The grade
of metamorphism lies within the pyroxene hornfels facies
(MM 50.119-123).
Formation
Baghdadite is a product of high-temperature skarn formation and is considered to form
by a reaction involving the pre-existing wollastonite and
calcite in the country rock and zirconium evolved
from the intrusive igneous liquid.
4CaSi03 + 2CaC03+ 2Zr02 →
Ca6Zr2(Si207)2O4 + 2C02
(MM 50.119-123)
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