I've heard (and after googling for a while, found) that the only difference between matter and anti-matter is simply charge. This bothers me when it comes to the neutron. Matter and anti-matter annihilate when they come together, so in the case of the neutron, what we'd have is just two neutrons coming together; that shouldn't result in anything like a positron and electron- the neutrons are exactly the same!
I can think of two solutions to my doubt. 1) There are other 'subtler' (not so commonly mentioned) differences between matter and anti-matter that would differentiate between a neutron and anti-neutron. 2) Maybe the reason the neutron and anti-neutron annihilate is that the quarks they are made from change (instead of having two down and one up quark, the anti-neutron would have two anti-down and one anti-up quark?). This seems like the most logical explanation to me, although it's kind of strange; the individual quarks would 'do the annihilation', not the neutron itself. Is this what's going on?
Sorry for my ignorance- I know almost nothing about the subject of anti-matter (or particle physics, or even barely any QM unfortunately).