Less commonly seen hones.

Through reading on this site, and doing a lot of research on the internet regarding sharpening stones in general, I have seen a number of different hones mentioned, but with little information on their use and other pertinent information, for example grit size, relative cutting speed etc.
So if any of the resident collectors/ experts could give any information on the following stones I would be most appreciative.
Cambrock silkstone, Cutlers Green Stone, Eldsborg or Norwegian Ragstone, Salmon Rouge, Turkish oilstone, Viking Whetsones and Wastilla Whetstonen.
Also, I have seen one reference to a Finnish stone which the owner seemed to think was a one of a kind and impossible to replace; I have tried researching Nordic stones and all I could find was the Eldsborg, Viking Whetstones and the Wastilla, does anybody have any idea what this other stone could be? It was mentioned in a thread which I believe was on knifeforums.com but I haven't been able to find it again.
Kind regards,
Alex

I have 2 of the Silkstones, maybe 3. I have not used them yet but will do so this week and then post a review in the hones forum and/or the Reviews forum.