My favourite crystals are amethyst and rose quartz....
As for precious stones ... I love Ruby's and also Sapphires. But unfortuneately I don't own any of those. Garnet is my birth stone, it is similar to a Ruby, but darker, it makes a nice and cheaper substitute.
I have a beautiful ( and I'm so bad because I can't even remember what kind of gem it is) but I think that it is a Topaz, or maybe aquamarine. Anyway, it is a beautiful aqua colour, I feel so relaxed whenever I look into it. It has an oldfashioned cut, with tiny diamonds around it. It has a really ethereal energy about it. So it would have to be one of my favourite stones
It's a toss up between garnet, hematite, malachite and yes... the good ol' plain black onyx (there's nothing nicer than a high-lustre polished onyx carving!)
amethyst will always have a place in my heart. purple is my favourite colour, and I think a piece of tumbled amethyst was my first ever stone. my father has also given me 3 items of amethyst since childhood, and they are just so beautiful. and the first 3 letters of it are the first 3 letters of my name, yay! (plus 3 is one of my favourite numbers!)