[Kelly Pedersen]

Well, in the slightly more interesting department, it could be a natural Powerstone aspected towards the demon-summoning Necromancy spells, or heavily quirked towards summoning demons.

Hmm. Other options:

• Each piece is somehow tied to a demon, and having it while you cast a summoning spell is the equivalent of knowing that demon's True Name.
• Along the same lines, each piece might let a specific demon reach out and contact the holder, whispering forbidden knowledge, dark bargains, etc. in their head, trying to get themselves summoned.
• Trinitite might be a natural source of mana, capable of raising the mana level in any area it's brought to by a bit (this could be a full level, or you could subdivide it more finely, reducing the penalty for Low Mana by only -1, for instance, or, in normal mana areas, letting non-mages cast spells, but at -4).
• It could be a "natural magic item" material - when integrated into the structure of an enchanted item, perhaps it provides a certain amount of the energy required to enchant it for free. Or counts as a Power enchantment on its own!
• You could play up the "transformation" element, and have it be a useful component in things that change one type of substance to another - natural Powerstones for Earth to Stone spells, for instance. Or maybe holding on to a chunk of it for long enough could actually transform a human into something like an earth elemental - a magical being with crystal flesh, gemstone eyes, etc.