Being a natural whetstone, each is different. When I ordered mine from China (about UD$30 including shipping), I asked the vendor to select a stone with minimal inclusions as it was to be used to finish straight razors. He replied that he couldn't guarantee anything but would try his best.
Here is what I received after lapping flat and chamfering the edges. Size is about 200mm x 75mm x 30mm.
Since receiving this whetstone about a year ago, I have used it on SRs of many different steel types. I have found it to be a slow but very fine cutter. For me, it excells particularly with harder stainless steel SRs. It takes a lot of time to properly finish an edge with this stone but I feel that the end result is worth it. Maybe I was just lucky with my purchase.
For harder high carbon steel blade, I tend to favour a hard black Arkansas finish while other high carbon steel blades tend to do well on coticules.
