I want to make up a few original gems for my world but I'm not sure what properties to think about. I already have a list of a few things I found online but it either feels incomplete or confusing.
I have things like hardness, cleavage, fracture, luster/shine, clarity (which I'm still trying to understand) rarity and colour. Two that I don't fully understand is refractive index and dispersion and I'm not sure how relevant they would be to creating a new gemstone.
My goal is to have some gemstones for jewellery or magical purposes like charms and amulets and spell ingredients, that sort of thing.