I finished lapping the black ark from them. It feels like glass at 600 grit sic. So does the trans black, but I think the trans isn't perfectly flat. Can't fit a sheet of paper under it on the granite but against the black and the straight edge their is a small amount of light. Paper thickness not as thick as a business card though. Might order some 80 sic and more 120 and try to get it perfect.I suspect the presence of Hematite in the Dunston might be the reason for it's higher than expected SG.