Non-standard stones for honing

Okay. So there are some stones that are commonly used around these parts. The 4k/8k Norton seems to be the Merkur HD of hones, and then there are the other Nortons, the DMTs, the Belgians and the Thurigan group (and then various other stones like the Arkansas, Japanese and Chinese stones and the O'Shanter).

But this thread about gratewhitehuntr's (possibly) sodalite hone made me wonder, has anyone here ever tried other minerals as hones? I was thinking it would be important to get quite a large surface because of the blade length of a straight razor, but gratewhitehuntr seemed to be able to hone up a razor pretty well on his natural stone despite the mix of the blue stuff and the quartz.

I'm sure there are many minerals that would make great hones not to mention rocks too the only problem is, do you want to test thousands of specimens to find a good one or use what has already been demonstrated to be superior and has been used for a loooong time? When you obtain a solid diamond or sapphire about 8x3 let me know. I'm sure it would make a great hone.

No, I don't want to test thousands of specimens (at least not at the moment). That's why I'm asking if anyone besides gratewhitehuntr has tried anything for honing beyond what's been labled as a hone. I was just curious if other people had experimented.

As I mentioned, it isn't necessary to get a solid piece of one material, and it's definitely not necessary to have a huge 8x3 slab.