Unlike the soft oil-shale, I've been preparing this Knightia from a much harder matrix. It's still oil-shale but doesn't seem to flake off as easily as the other. I love how I can see the specific bones and the scale is a bonus. Here is my question to the frum: The dental tool shown in the photo is what I've been using but it doesn't seem to be able to get that final bit of matrix off. It looks like it's covered in a thin layer of dust and I'm worried that if I scratch it off, I will lose much of the detail.
How do I remove the final layer and get that dark brown carbon color that makes me proud to show off my work?!?