This is a pretty simple question, but I'm stumped. I know Gryffindor is ruby, Ravenclaw is sapphire, and Slytherin is emerald, but there seems to be no official gemstone for Hufflepuff. Various online sources say it could be a yellow diamond, a yellow garnet, topaz, amber, or other things which I've never heard of (I don't know anything about stones). Any opinions? I mean, what sort of stone is both yellow and in the same league as rubies, sapphires, and emeralds?

I'm hedging on just going with topaz, but I don't know what its plural is...topazes? topaz stones?