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Yeah if the left stone is harder to lap than the right one it's doubtful we have a CF and a Welsh slate.

Hmm Welsh slate isn't that hard either, we will need better pictures :) Try taking pictures in the shades for a better contrast of the stone.

A CF is a Charnley Forest Hone, often olivegreen with...

Based on size and colour I would guess Welsh slate at the left and a light green Thuringian at the right. To be sure it's Welsh slate you can compare it to close-ups of Dragon's Tongues and Yellow...