Help indentifying rigid insulation

I picked up what looks like some rigid insulation sheets for free from someone on Craigslist here. They are 4 foot by 3 foot by 1 inch. It looks like rigid mineral wool. It's not flexible like mineral wool batts and it doesn't really feel like fiberglass. It's dark green in color and heavily compressed. It's pretty rigid, but not hard to the touch, and you can pull it apart. It's also really dense. Each 4'x3'x1" sheet weighs about 11.6 lbs. If my math is correct that's 11.6 lbs/cubic foot. That's much heavier than anything I've seen. So I'm not sure what I'm dealing with. So I'm wondering, if it is a really dense insulation do you think it would it work for acoustic panels, bass traps, etc. I haven't seen any coefficients for anything like this. I've got 40 sheets so I could make quite a few panels. I would be using then in a 10' by 14' room, accross corners, on walls, and on the ceiling. Any help would be appreciated. Thanks, Jeff

It could be Thermafiber, which is made in the US from recycled materials. http://www.thermafiber.com/default.asp?PageIndex=526

Thanks, John. After searching a bit more it looks like a few companies (Thermafiber, Roxul, IIG) make an "Industrial Board" that is a compressed mineral wool that is used for high temperatures. They go all the way up to 12 lbs per cubic foot. It looks like that is what I have. No one gives the Coefficients for boards this dense, but I think I will go ahead and try them out. Thanks