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Locality of columbite from Madagascar - Analalava vs. Tsaramanga

Posted by Pavel Kartashov  
Pavel Kartashov July 12, 2012 01:25AM
I'd received crystaline cluster labeled as "Ferrocolumbite from Analalava district, Sofia region, Mahajanga pr., Madagascar".

But locality don't contain any pagmatite minerals but only mineralized basaltic effusive rocks.
Fromother hand, here was uploaded photo very similar crystal -

Other very similar crystals we see in classic pegmatite occurrence
Compare my specimen with

I am confused...:-(:-S:-(

By the way my mineral in reality is Sc-bearing ferroan and titanoan Manganocolumbite. It contains inclusions of quartz, microcline, films of bastnasite-(La), pseudomorphoses of bismuthite after bismuthinite and overgrown by minute tetragonal prismes similar to xenotime.
open | download - MINS6922_COLU_i.jpg (94.3 KB)
open | download - MINS6922_COLU_0.jpg (84 KB)
open | download - MINS6922_COLU_1.jpg (136.3 KB)
Knut Edvard Larsen July 12, 2012 09:09AM
The labelling of these as coming from Analalava District, Sofia Region are highly doubtful, i i would say a misnomer.
The geology of the Analalava District consist, as you say, only of cretaceous basaltic roks and jurassique-cretaceous and tertiary sedimentary layers. The columbites like these come from precambrian granite pegmatites (55o MA) from the socle of the Madagascar highland. There are so far as I know no granite pegmatites in the Analalava district,. and none marked on the geological maps of the area.

There is a granite pegmatite field with Beryl-Columbite subtype LCT pegmatites in the neighbour District of Analalava, in the Bealanana District , along the River Meavarano wich produced some columbite in the 1950s, but I have not seen these.

Your sample looks indeed very similar to samples from Tsaramanga. I have several in my collection, collected at the Tsaramanga pegmatite. Together with these I found also bismutite pseudomorphs after bismuthinite etc.

But , of course i can't say with a 100% certainty that your specimen is from Tsaramanga. It may come from another locality- but not Analalava District.
Knut Edvard Larsen July 12, 2012 09:54AM
Message sent about
Pavel Kartashov January 10, 2015 02:20AM
Michel never answers messages and complaints.:-D But it looks like, that we both had the same source of material.
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