Early in the film, we see Thomas Harewood drop the said ring into a glass of water which reacts violenty and creates a massive explosion.
What made the ring into a bomb?
This post on reddit includes a suggestion:
...it was a TINY amount of antimatter suspended in a TINY magnetic field in the ring. When the ring dissolved in the water, the containment failed and the small amount of antimatter reacted with the water/ring remains/etc.
Is there any evidence to support this?