Re: Why place warp cores away from nacelles?
Perhaps Dilithium initially is just a form or variant of lithium. It's travelling through space on an asteroid or comet, and said asteroid or comet interacts with subspace in some way (a subspace pocket, a breach in subspace, etc.). Through that reaction, it changes the nature of said lithium creating dilithium. Then it hits a planet where it's mined. This would makes sense considering in TOS dilithium was a rare element.
Because it phases into subspace and is bombarded with intense radiation in the process, when antimatter and matter collides with it the the crystal phases out of space time and partially into subspace, which phases the created plasma as well, which makes it the perfect fuel to create subspace fields. That also explains why the crystal doesn't annhiliate when matter and antimatter hits the crystal.
Just a theory, but one that at least partially fits onscreen evidence.
I like this theory.
"If you can't take a little bloody nose, maybe you ought to go back home and crawl under your bed. It's not safe out here. It's wondrous, with treasures to satiate desires both subtle and gross; but it's not for the timid." - Q