Named after a substance from the 2009 film Star Trek, a Red Matter Explosive is a very deadly variant of implosive, crafted using the hard-to-obtain Strange Matter with an Antimatter Explosive in the center.
When detonated, it will create a black hole and start sucking in everything nearby. Blocks are then turned into entities and fly around the black hole, creating a crater that slowly grows in size. The only way to stop the black hole is to detonate an Anti-Matter explosive or missile at its core, which will be sucked in from a much farther distance or detonate a Hypersonic Explosive or missile near but it is very dangerous but it will move it to another direction or upwards that will cause it to fly away from the land. Because performing this process will create a considerable explosion, it is suggested to keep at least a 100-block radius clear from the center of the hole.
The Red Matter explosion will eventually stop on its own and NOT, as many seem to think, destroy the world. One can however with another explosion set off nearby, set it on a course of destruction - Great if you want to build a massive underground base. Although the red matter bomb is known for destroying worlds, it stops destroying the world after about a 1000 block radius But leaves a bit of devastation. Found out by accident, two black holes colliding explode and disappear into nothingness.
As of yet, there is no way to build a shelter immune to the effects of red matter explosions. Even hardened brick or Blast Proof Walling is unable to hold any T4 explosion at bay. Go to  to see a Yogscast 'demonstration'.