Quote Originally Posted by Dinnova
Quote Originally Posted by demonicsephiroth
It was used to summon Meteor and it itself became meteor
That could be true, but it getting destroyed when holy was cast or when sephiroth was defeated seems more likley. Materia just gives you the knowledge to use the attacks.
Actually, no, that can't be true. Ignoring the fact that the Black Materia becoming Meteor makes no sense on a variety of levels, the fact remains that the game specifically elucidates just how Meteor magic is brought about.

Aeris: ...this must be magic. Just what Sephiroth was saying. The Ultimate
Destructive Magic, Meteor. It finds small drifting planets with its magic. And
then collides with them. This Planet might get wiped out entirely...
As one can see, the Magic finds a preexisting object to collide with Gaia.

As to the actual fate of the Black Materia, it unfortunately remains unknown. Since the Advent Children Spoilerconcept of the Negative Lifestream only came about as a consequence of Geostigma, and that the Black Materia seems to interact with Gaia, it seems likely that the Black Materia is derivative of the Gaian Lifestream. That being the case, it's unlikely the Materia was destroyed. It's possible that the supercondensed Spirit Energy was somehow diffused back into the Lifestream, but (without further knowledge) it seems most likely that it is still extant.