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


Alexkhomyakovite is a relatively new mineral, approved in 2015 and to date (March 2024) reported only from the type locality.


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

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