D&D mechanics split it into two different metals:
Mithral (yes, spelled that way): As steel, but lighter, and that's about it. Appears silverish.
Adamantium: Lighter than steel, but not as light as mithral. It is also significantly more powerful than steel. Appears black.
Is it just me, or in the LotR movie, wasn't Frodo's Mythril vest silver as opposed to black?
Man, everbody copies the old professor, don't they? And as for Frodo's vest, yes, it was silver. I was referring to Pippin's uniform of the Tower Guard. They had mithril, too, though only on the emblems and the like, I think. As for Adamantium... well, that's just good old Adamant, and they are trying to make is sound like an element or mineral with the "ium" ending. Personally, I like Adamant better. Supposedly it's either diamond or lodestone, actually, as adamant only ever occurs in legend. And as far as the Denadorite, being the subject of this topic goes... well, I don't think that there's much more to say. It's pretty well Quartz, unless I miss my mark. That's VERY hard (7, or something like that?) but I think would be quite flawed as a weapon because it could break. Unless, of course, enchantments bound it...