I'm inclined to belief Mario on that one. They've been around for a very long time and they sell to multiple different markets.
That said, Mario isn't and never has been Tom's "partner". Tom is just hoping to get a commission on sales made to customers he directs to Mario. He has operated out of Mario's tent in the past and iirc, that ended badly.
His reference to "museum quality" relates to Mickey Granillo's stones and he hasn't yet given Tom a price for the high quality stuff. Tom is talking about $50-$150/lb (per pound, not per piece) for something different. In true flim-flam man fashion, he says that museum quality with a certain provenance can fetch thousands (true) but doesn't explicitly say that such pieces are what will be for sale (without such provenance they're worth fuck all) and he doesn't even know the miner's qualifications or whether the stones have been certified.
"Engineer" is rapidly becoming the most abused term of the decade, but I can see no evidence that Mickey describes himself that way.