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Formula: (Mg,Fe3+)2(Ti,Fe3+,Al)O4
Multiple oxide, ulvöspinel subgroup,
oxyspinel group,
spinel supergroup,
titanium-bearing mineral, forms a series with
ulvöspinel
Crystal System: Isometric
Specific gravity: 4.03 measured, 4.04 calculated
Hardness: 7
Streak: Black
Colour: Black
Solubility: Soluble in hot hydrochoric acid, but only partially soluble in cold hydrochloric acid, hot sulphuric acid
and hot nitric acid
Magnetism: Strongly magnetic
Environments
Carbonatites
Metamorphic environments
Qandilite is a member of a complex spinel solid-solution series. These complex
spinels are restricted to
carbonatites.
Localities
At the Kangerlussuaq complex, Kangerlussuaq Fjord, Sermersooq, Greenland, Denmark, qandilite has been found in a
periclase-forsterite
marble in contact with an alkalic
ultramafic rock intrusion of Caledonian age (490 to 390 million years ago)
and co-exists with spinel and
geikielite
(MM 49.739-744).
At the type locality, Dupezeh Mountain, Hero, Qaladiza, Pshdar District, Sulaymaniyah Governorate, Iraq,
qandilite is found in a forsterite
skarn in contact with a banded
diorite composed mainly of
andesine and kaersutite with
ubiquitous titanium-bearing augite,
titanium-bearing magnetite and
ilmenite. The forsterite
skarn is buff to cream coloured, coarsely crystalline and has a granular
texture. This rock is heavily impregnated with dark-coloured qandilite,
perovskite and spinel which are
homogeneously distributed throughout the rock.
The forsterite skarn is
composed of 74.2 % forsterite, 17.7%
calcite, 3.4% spinel, 3.0%
perovskite and 1.7% qandilite with accessory
calzirtite and thorianite.
Calcite is often found in small lenticular and irregular pockets forming the
interstitial matrix between the coarse idioblastic (referring to metamorphic rocks in which the grains display fully
developed crystal forms) crystals of forsterite. The closely associated
qandilite, perovskite and
spinel also occur in the interstitial matrix between the
forsterite grains as an alternative to
calcite. Qandilite is found in a variety of textures; in most cases it
mantles perovskite and spinel and
occurs intergrown with perovskite. In some instances it occurs as euhedral
grains embedded in the calcite. The grain size of qandilite varies from 0.1 to
2.3 mm.
It is suggested that qandilite developed at a late stage of thermal metamorphism by introduction of Ti from the
adjacent titanium-rich dioritic
magma
(MM 49.739-744).
Qnadilite from Dupezeh Mountain - Image
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