Every time I hear about a black hole, it's always in conjunction with the collapse of a star. Have any other processes been observed to create a black hole?
There are currently three classifications of black hole and these are stellar, super massive and miniature.
Stellar black holes are formed by a massive star collapsing and its mass being great enough to form a black hole of moderate size
These black holes can have the mass equivalent of a billion suns, these most likely exist at the centre of galaxies and are probably as old as time itself.
Miniature black holes are theoretical and are thought to have been created at the early stages of the universe. these require masses less than that of our sun and are thus very unlikely.
"But Rhys" I hear you cry, "these are all from stars you fool!"
And yes, yes they are, this is because black holes are formed from mass, and lots of mass (except miniatures), coincidentally large amounts of mass tends to gravitate towards each other and form stars long before it forms black holes.
Therefore theoretically, a black hole does not even need stars, it just needs lots and lots of mass, but having that much mass without forming a star is no easy task.
Short answer, you can make a black hole from anything as long as it has enough mass, but good luck stopping this from forming a star beforehand!
Well, when two black holes collide a new black hole is created. You could call that cheating, but this process is very different from that of a star collapsing. Also, these guys would be after your skin if you did.
When two black holes collide, there are three stages. Firstly, there's the "inspiral", which is exactly what it sounds like — the two black holes slowly spiral in to each other. Cue waltz music. Then there's the "Coalescence", where the two black holes merge. Note that prior to the merge, their absolute horizons actually grow in size, as if in anticipation of the merge. The exact behavior of the coalescence stage is not well understood yet. Finally, there's a "ringdown", where the new black hole (currently shaped like an eight) shakes down into an ellipsoid.
This has not been observed, but is something we're pretty sure occurs.
There also are primoridial black holes, from the time of the creation of the universe. They are extremely tiny (and unstable), though I doubt they can be formed at this current era.
It is theoretically possible to create black holes with radiation, it is called a "Kugelblitz". The technology needed to create bright enougth pulses of gamma radiation is beyond our current technology, but may be possible.
The possibilities for the usage of such miniature black holes are enormous, it would solve all energy problems because they can convert between 20% to 50% of the introduced mass directly to energy. If the hawking radiation exists its possible to get 100% but enougth scifi.
Micro black holes are believed to exist, coming into existence for a very brief period of time following high energy particle collisions. Some theorists believe that this may occur naturally in Earth's atmosphere due to cosmic rays. I read a statistic somewhere which said that at any given time there would be three black holes in our atmosphere due to this process (if it exists).