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Formula: CsLi2Fe3+Si4O10F2
Phyllosilicate (sheet silicate), trioctahedral mica group
of the mica group, cesium-
lithium- and fluorine-
bearing mineral
Crystal System: Monoclinic
Specific gravity: 3.33 measured, 3.342 calculated
Hardness: 2½
Streak: White
Colour: Colourless
Luminescence: Luminesces pale yellow under short wave UV
Environments
Pegmatites
Carbonatites
Metamorphic environments
Kreiterite is a new mineral, approved in 2019 and to date (February 2025) reported only from the type
locality.
Localities
At the type locality, the Dara-i-Pioz Massif, Districts of Republican Subordination, Tajikistan, outcrops of the
massif are extremely inaccessible and most mineralogical research is done on material collected from the
associated glacial moraine. The central part of the massif is composed of
aegirine syenites and
fenites. The outer rim is composed of binary (containing both
muscovite and biotite)
tourmaline granite. In
the eastern part of the massif there is a stock of coarse-grained
cancrinite
foyaite.
There is rich and diverse rare metal mineralisation associated with the
widespread alkaline pegmatites,
fenites and
carbonatites of the massif. One of the characteristic
features is the variety of the mica group minerals
muscovite, annite,
polylithionite,
sokolovaite, orlovite,
garmite, gorbunovite and
kreiterite.
Another characteristic feature of the massif is cesium mineralisation. There
are about 30 approved cesium minerals worldwide, of which at least 13 occur
at the Dara-i-Pioz Massif: kupletskite-(Cs),
telyushenkoite,
zeravshanite,
senkevichite,
kirchhoffite,
mendeleevite-(Ce),
odigitriaite,
mendeleevite-(Nd),
fluorapophyllite-(Cs), the four
cesium-dominant members of the
mica group: sokolovaite,
garmite, gorbunovite and
kreiterite, and, in addition, there are three more cesium-bearing
minerals from this association: yusupovite,
letnikovite-(Ce) and
kalyuzhnyite-(Ce). As with the other
cesium micas occurring here,
kreiterite was found in fragments of lumps (up to 2 m in size) of a rock composed mainly of granular
quartz. Kreiterite occurs in polymineralic
quartz-pectolite aggregates (from
1 to 15 cm in the largest dimension), sometimes embedded in this rock. These aggregates consist of
manganese-bearing pectolite,
quartz, strontium-bearing
fluorite, aegirine,
polylithionite, datolite
and minor rare minerals. Kreiterite is very rare and is distributed unevenly in the
quartz-pectolite aggregate. Most
commonly, kreiterite aggregations are confined to the boundaries of
aegirine with quartz, or, rarely,
pectolite. Kreiterite occurs as fan-shaped clusters of lamellar
grains and as small accretions in aegirine crystals.
Kreiterite is colourless in individual crystals and white in aggregates. It has a white streak and is
visually indistinguishable from other light micas. The lustre is vitreous to pearly, cleavage is perfect and the
flakes are flexible
(CJMP 63.1.103-110).
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