http://www.mindat.org/photo-23579.html this is not listed as occurring here http://www.mindat.org/loc-2689.html Should it be or is this misidentified. 
Of course this isn't belyankinite, but some later product of komarovite alteration (mixture of pyrochlore and rhabdophane?). 
This specimen was acquired from, and has been identified by, Nikita Chukanov in Moscow. I have no reason to doubt the information given on the identity or provenance of the specimen. It was collected in the 1990-ies, and entered into the Mindat database in 2004. Dear Bertil,
In this particular case I more believe to my own eyes. Different cases occurs, but this one is obviously clear.
Belyankinite grows in an another zones of pegmatites of another type. Your specimen is from natrolite (apoussingite) core of agpaitic raremetal (Nb-Th-Be) pegmatite #61. Belyankinite grows in more simple situations - usually in intermediate aegirine zones of pegmatites.without ussingite core or visible ussingitization.
Lomonosovite from border zones of the pegmatite #61 is transformed/altered not far than into murmanite.
Of course you may not make any changes in description of your photo - this is your right, but in this case I will be forced to allow this photo for display in your personal photogallery only.
Pavel 
Bertil: Probably best to notify Nikita and ask for his comment in this thread. As suggested I got in touch with Nikita. He has no recollection of this specific specimen, as it was so long ago. So he could neither confirm nor dismiss the authenticity of it, judging from the photo. He needs to see it with his own eyes.
I have also gone on to consult the literature. Pekov (Lovozero Massif, Moscow, 2000) states that belyankinite is widespread in the Lovozero massif (citing Gerasimovsky and Semenov). Besides the type locality, Pegmatite No 13 (Gerasimovsky 1950), belyankinite has been found in the following places: Mannepakhk, Flora, Karnasurt, and Kedykverpakhk (Semenov, 1957, 1972), where it occurs in hydrothermally altered rock as pseudomorphs after murmanite, i.a. associated with decomposed nepheline, altered to zeolite minerals.
On closer examination of the specimen in question, it is obvious that it constitutes pseudomorphs of murmanite, platy crystals of which transsect the specimen (I shall upload some close-ups).
Given the original labelling, the literature on belyankinite available, and the properties of the specimen in question, I would say it actually is belyankinite from Karnasurt.
Bertil,
I don't speak that belyankinite absent on Karnasurt Mt at all, I say it absent in your specimen. There is difference.
I don't need in your naturphilosophy and literature searchings because of I well know the pegmatite from which your sample originates.
Nikita also know it and, frankly speaking, his reaction was quite predictable for me (I know him 25 years).
There are a lot of small moderately evolved pegmatites on Karnasurt with primary lomonosovite. During their alteration big quantities of murmanite forms. In some cases this murmanite is replaced by belyankinite. But this occurs comparatively rare and forming belyankinite is "mineralogical", collectors don't take it (similar way practicaly nobody take quartz from Bastnas mine for quartz itself). The main pegmatite producing high grade belyankinite for collections located comparatively close to Karnasut, over the pass El'morajiok - http://www.mindat.org/loc-23263.html
Pegmatite #61 is large, evolved pegmatite with natrolitized ussingite core. Only 4 so large pegmatites are known on Karnasurt Mt. They are very popular besides collectors, and every from these pegmatites has well recognizible pecularities which allows to understand origin of specimens.
There are a lot of fine-tabular murmanite in Northern border zone of pegmatite #61. But it is quite fresh, pinkish-brown, with strong lustre. If it is replaced by belyankinite, this process is on only initial stages - microamounts on surface of its agregates. Nobody need in belyankinite or murmanite of such quality.
Your sample is from natrolitized (former ussingite) core of the pegmatite. Primary lomonosovite group mineral was here represented by vuonnemite invariably. So all products of its alteration are high niobian - epistolite -> komarovite -> pyrochlore +/- niobian members of nenadkevichite group. You would faster find here gerasimovskite rather than belyankinite.
Your additional photos shows pseudomorphoses after vuonnemite replaced by epistolite (yet not begun to replacing by komarovite). No belyankinite here.
