I have two bkack coral slices ( cut for pendants) from a black coral 'tree' that was harvested more than 50 years ago. We also cut a lovely organic piece of the stem and polished it as a pendant. The markings on black coral are very much like a tree and glow in tones of rust and brown. The markings on my two pendant /slabs aee still white from polishing powder because they've been in storage all this time are were never cleaned after the buffing process. ...but your markings have darkened naturally to a golden brown. Beautiful!