Images
Formula: K6(Ca2Na)(CO3)5Cl.6H2O
Hydrated carbonate
Crystal System: Hexagonal
Specific gravity: 2.25 measured, 2.196 calculated for the empirical formula; the difference could be caused by
micro-inclusions of silicate minerals with higher densities than alexkhomyakovite
Hardness: 3
Streak: White
Colour: Colourless, white or grey
Environments
Alexkhomyakovite is a relatively new mineral, approved in 2015 and to date (March 2024) reported only from
the type locality.
Localities
The type locality, the Koashva Open Pit, Koashva Mt, Khibiny Massif, Murmansk Oblast, Russia, alexkhomyakovite
is an apatite deposit. Koashva is famous for the numerous peralkaline
pegmatites mainly located on the margin between
urtite and
nepheline-apatite rocks. More than
160 different mineral species are found there, including 27 for which Koashva is the type locality.
Alexkhomyakovite was found in several pegmatite lumps,
uncovered in the zone of active mining operations. It is associated with
villiaumite, natrite,
K-feldspar, pectolite,
sodalite, biotite,
lamprophyllite, titanite,
fluorapatite, wadeite,
burbankite, rasvumite,
djerfisherite, molybdenite
and an incompletely characterised sodium-calcium silicate. White powdery aggregates of
thermonatrite, villiaumite,
fluorite and sylvite are products of
the supergene alteration of
natrite, alexkhomyakovite and
primary red
villiaumite, which are unstable under atmosphere conditions.
Alexkhomyakovite occurs mainly inside massive polymineralic
pseudomorphs after large (up to 3 x 5 x 15 cm3)
delhayelite crystals. Alexkhomyakovite is an important constituent
of these pseudomorphs; in all studied samples it occurs in intimate
intergrowths with other phases, mainly pectolite,
villiaumite, K-feldspar and the
incompletely characterised sodium-calcium silicate. Monomineralic areas of alexkhomyakovite in such aggregates
are typically not larger than 10 x 20 microns. Massive veinlets (up to 3 cm long and 1 mm thick) with
alexkhomyakovite as the major component are observed in the border zone of some of the
pseudomorphs after
delhayelite, usually at their contact with
natrite nests. These veinlets contain inclusions of fine-grained
villiaumite and fibrous
lamprophyllite and/or
pectolite.
In nests of beige or yellowish granular natrite, alexkhomyakovite was
found as separate grains and their clusters, sporadically abundant, included in massive
natrite. Both alexkhomyakovite individuals and
natrite matrix are saturated with microinclusions of
pectolite, lamprophyllite
and/or villiaumite.
Alexkhomyakovite is transparent to translucent, colourless in individuals and white or grey in massive
aggregates, with a white streak and a vitreous to greasy lustre
(EJM 31.1.135-143).
Alexkhomyakovite from Koashva - Image
Back to Minerals