"And into this ring he poured all his cruelty, his malice and his will to dominate all life."
All these things that Sauron poured into his horcrux added up to considerable mass-energy packed into a very small volume. The density was so high that the object gravitationally collapsed into a singularity. Sauron added rotational momentum, so it was a ring singularity, as found in a Kerr black hole.
No, you could not wear this ring on your finger. But it could be an extremely destructive weapon. Disappearing when wearing the ring represents leaving the universe when crossing its event horizon.
The One Ring being a singularity explains why it was so hard to destroy. Perhaps the only way to dispose of such a thing without it causing huge damage to its surroundings is to drop it into another black hole: Mount Doom.
The Lord of the Rings: In Space!