I need your guys help with this one. 

I bought it at a Gem Faire from a dealer in Pakistan (Skardu) minerals and he had the usual expected assortment of Skarduvian aquamarines, topazes, and a whole suite of minerals from that area.  So I assume this one is from there as well.  His prices were wholesale and relatively low, and he offered some really good deals.

I love all of those gemstones but this particular stone caught my eye...after I picked it up.  This thing is DENSE.  As in, it feels every bit as dense as galena and cassiterite- both of which I am familiar with.  It's considerable heft is it's most noticable feature- So as I picked it up I was inclined to think, "Ah, Cassiterite."

The dealer didn't know for sure what he had.  He simply shrugged and said, "Cassiterite huh, Well, that works for me I guess.  I'll give you a deal, 60 bucks for both that and the $40 Axinite you were eyeballing earlier" (I got both.  Other stone's identity was easy to confirm.)

So, I would be tempted to go with that ID- it doesn't scratch with a steel pick so it's hard enough, but a few things to question:  The crystals are rather distinctive- rectangular prisms here, mainly.  Cassiterite crystals tend usually to be more angled and pyramidal.  And these here are distinctively color toned- ruby red in the center and dark brown on the outside.  So I'm not so sure- it could be another really dense mineral, some kind of ColTan mineral perhaps, or something more sinister (I hope not, since I don't have a Geiger counter to test for that.)

Your thoughts?  Again, location is from Pakistan, hardness about 5-6-ish, specific gravity about that of cassiterite or galena, i.e. very heavy for it's size.  Is it cassiterite or some other mineral?