Scratching regular stone is fine, but please keep in mind the
Mohs scale when scratching things like gemstones! If you wanted to move the Jet stone to either a talon or his beak, Jet has a hardness rating between 2.5 and 4. There are other black gemstones and even natural black diamonds (called fancy black diamonds if you search for them) if you wanted to consider any of those (if you did want to move the stone either for his beak or a talon).
Also to clarify, "He has flecks of dark violet throughout his coat He has larger streaks of dark blue also through his coat between green" - are you describing the iridescence of his feathers? (First generation characters should remain close to their natural colors - melanism and leucism are ok though!)
Just wanted to note those two things. If you wanna keep his stone as is, just remember the Mohs scale when 'scratching' things. Otherwise, he looks great. A great spookyboye,
let's get spooky ~