As far as the working conditions of the miners, it is really more "blood diamonds" than "the Mangificent Seven".
A lot of has been documented about Ilakaka. If you are new to the story, a good place to start is the outstanding photoblog entry at the big picture:
(from BigPicture at the Boston Globe)
the journal "Le monde" and the BBC also offered their takes on Ilakaka and the tales of hellish working conditions and cutthroat capitalism.
This first video (in French) illustrates the genesis of Ilakaka and the unsuing violence. The second video shows that the promise of new wealth also brought increased prostitution in the region.
Bloggers also tell personal experience of Ilakaka.
Brice explains (fr) how people are recruited to be miners and then exploited by middle men.
Croc says (fr) that cost of living in Ilakaka is higher than anywhere else on the island (this for a town that had 40 people a decade ago).
Quinta Maconda shares a telling story:
"Ten thousand kilometers away, the whisper of “Bleu Royal”, reverberates with awe and glamour and never fails to cast a spell on the stratospherically rich when presented with a perfectly cut stone by one of Place Vendome’s prestigious jewelers. For us, hearing “Bleu Royal” spoken by shoeless Malagasy men covered in thick clay emerging from the bowels of the earth sent shivers through our spines.[..] when passing through Ilakaka, the infamous mining town of southern Madagascar in the province of Tulear, we had the urge to explore. Didier, our driver then, did not want to set foot out of the vehicle. He was adamant: “it is shear madness.”"