A Plea to All HP Ficcers
Somebody, somewhere, started the idea of Snape having "onyx eyes" - probably by mistake for obsidian - and countless ficcers who followed after have slavishly copied this. All please note: onyx is usually a greenish off-white with grey-green or toffee-coloured swirls. Black onyx does exist but it is usually a) streaky and b) artificially dyed - if you look at Onyx Sphere Corner you will see spheres made in fifty-three colours of natural onyx, only three of which are black and only one of which is a pure dense black. Horace Slughorn has onyx eyes. Snape does not. Also please note that only house-elves, cats, owls and nocturnal lemurs have "orbs" - other people just have eyes.