For some reasons I can not open all the pictures but from what I have seen I can say.
The lighter coloured stone could be CF. If you look near the chip near to one of the narrow side there is small crack line which to me shows so called translucency. The same think in my book shows that it is not a slate.
In past I had CFs which would not improve edge from my Thurri.
The best thing would be to compare face to face with others. One of such occasions could be London Razorcon in November. There should be enough CFs and philistines to discuss and compare it with.