That is correct. He did a great job carving it. I was also looking for some rock work in a 55g when I came across gray feather rock at the landscapers, but passed it by. His thread resparked my interest in that stone and I thought I would ask my aquatic peers if they have positive results to put to rest any reservations. ...cause this place rules.
You do need gloves and eye protection to work with it but as long as you hit it with some 80 grit sand paper it will smooth out and not be that rough .When working with it as you carve the shards turn to a sand like substance .Plus after a while in your tank algea will grow allover it and be smooth .PLUS due to the extreme porosity of it think of how much aditional area you will have for your bacteria to grow
I tried it and all the above is true. I also had some issues with waterlogging it prior so it would sink. I thought it looked great but when the bigger fish got spooked they kept tearing themselves up on it. Finally removed and am tossing around some ideas for smaller fish decor.
The easiest way I found to water log it is to boil it .That way it kills all bacteria before it hits your tank and fills all the little air pockets with water to make it sink also java moss loves to grow in this stuff .If you are worried about fish injury you could always put some in a bucket with some java moss out side till the rock is covered with the moss. This type of rock is realatively new to me also so we will see how it goes.
Good luck with it. I know it is fairly popular around here. One of the lfs sells pre carved pieces attached to slate for 60-90 bucks. The same sized uncut rock is 9 bucks at Lowes.