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A while back I read a short story about this alternate dimension story where these aliens had figured out how to trade resources with our earth by shunting materials across dimensions...on earth's side their material manifests as tungsten, I believe, although I remember there were side effects of the shunting that were potentially dangerous. I think they had also figured out how to communicate...I can't remember a lot of the details. The aliens were some kind of underwater creature but it doesn't go into a lot of detail about their immediate environment. The story describes them floating around but omits other details.
Most of the story surrounded these 3 sort of "gamete" children/adolescents. These aliens had three types of young that, when "joined" after maturity (a sort of pseudo-sexual union of the 3 types of gametes), formed an adult. After a trial period of temporary joinings the gametes fuse permanently and complete the life cycle (I can't remember if the adults produce gametes asexually or what). The adult alien's consciousness is wholly independent of the gametes, who lose consciousness when joining and disappear as independent entities once joined. Adults keep the truth of "joining" secret from the young, who believe they merely grow into adults individually.
A main feature of the plot is that the particular gametes of the story have heard about a "new adult" that was some sort of genius and who was up to no good with respect to trading with the human world, and they never discover that the "new adult" is actually the product of their own joining. The last time they fuse (for good), the reader discovers that they, in fact, are this "new adult" they've been learning about and trying to sabotage.
Anyway, I was trying to describe the plot to my fiancee and I can't remember the title or the author, and searching for it on the internet is not fruitful.