I know I asked about some of this in my other thread, but a dedicated thread for this particular subject seems more sensible. In short I've had a tiny, 10k green stone hone for some time and have been trying to find a larger one. Finally the seller is now stocking both a bigger version of this one, and similar hones in other grits. However very little information is available on these stones. I'm eyeing four of them (1.5k, 3k, 6k & 10k) which are labelled as being onyx, ruby, agate and green-stone.

I'm curious as to whether anyone has experience using these materials? I can provide images: Onyx (1.5k) Ruby (3k) Agate (6k) Green Stone (10k) as said I have some experience with a smaller version of the last one. It's very glassy and hard. I've used it for polishing razors and sharpening knives (the latter requires a fair bit of force and a circular stroke) but its performance is difficult to gauge as the size limits how it can be used.

I find them very attractive and am very tempted to purchase them (in addition to some more conventional hones) but their hardness concerns me. The seller claims they are good for razors, but I take this with a grain of salt, and would love to get any feedback I can. If no-one has any direct experience I'm open to opinions. I don't mind giving it a shot and reporting back provided no one thinks it's a really bad idea.

So can any experts give their opinion on hones like this, whether they're advisable for use with razors?