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"Cutlers green hone - is of so hard and close a nature, that it is only applicable to the purpose of cutlers and instrument makers for giving the last edge to the lancet and other delicate surgical...

If it is the stome product 'Dragons Tongue' as advertised on the site then it would appear that it is suitable hone stone quarried from veins in the slate mines (as quoted from Tucker above).
I am...

Here's a bit from Tucker, G, 1983 Ayrshire Hone stones.

"Hones were also made in North wales. Knight mentioned 'Idwall oil stone'; this comes from the Llyn Idwal in Snowdonia, but the hones...