No it is not slate board it is a pressed wood product with resin etc mixed in it. Looks similar to OSB but thicker and smoother (tongue and groove). I discovered it when I build my new house. It was a very large floor plan 11,000 sq ft. that could not be under roof quickly it was going to be exposed to rain and weather for a extended time. So it was shown to me by commercial construction supplier. It is not carried by HD
etc. that I have ever seen. I just happen to have about 15 sheets left over and that is why I used it. Works great and supports lots of weight. Lumber yards in your area should carry it. Like I said before, I would not sheet it unless you have a acrylic tank.