Le 30 avril 2008, par Jeff,
Carbonatites are the most ridiculous type of igneous roks in the world : mostly made of igneous carbonates. In the ca. 1.2 Ga Phalaborwa pipe (NE South Africa), they occur in association with some other alkaline rocks, for which I do not have photos yet.
The carbonatite itself contains mostly carbonates but also garnet, phlogopite and possibly feldspathoids.
The complex is mined by no less than three companies, PMC (Phalaborwa Mining Co.) mines the copper-bearing carbonatites in the core of the pipe, and digged the big hole that is quite prominent in the landscape. Foskor mines phosphorus, from apatite that occurs in apatite, in the pyroxenites around the pipe (so they are effectively processing the "refuse" of PMC mine !). And vermiculite (a phyllosilicate with useful thermal properties) is mined, from phlogopite pegmatites.
Les adresses correctes sont de la forme http://jfmoyen.free.fr/spip.php ?articleXXX
Les adresses correctes sont de la forme