Also from the same page referencing non evil uses: "Onyx was a common stone among the drow, a gem worn by drow of average station, albeit they used only black ones."
They are eeeeeeeeeevil. Chaotic Evil, to be precise.
Not denying that most Drow are evil but the act of wearing the stone seems more to me that they just like the way it looks
Same deal with spiders, come to think of it: association. In and of themselves, spiders - like onyx - aren't technically evil, but between the two there's such a common association with manifest evil that you can expect most folks to at least keep others indulging in related imagery at arm's length. Overall, there's more bad than good when it comes to onyx (especially in certain contexts).
