Guild Wars 2

I bought some but can’t put them on my armor. I’m pretty sure I’ve seen people use these instead of Runes.

I thought maybe I couldn’t use them because I already had Runes on, so I bought a lvl 80 piece of armor with an unused upgrade slot, but I still couldn’t apply it. What gives?

You can only use ruby orbs on armor. You can use the exquisite ruby jewels on amulets, earrings, rings, and the back piece.

Crests are used on armor, you cannot use jewels. You can use unmanufactured precious stones though. Keep in mind that crests and orbs are stat equivilant.

http://wiki.guildwars2.com/wiki/Crest