I'd never heard of it before.

Its a cement based product, which usually makes for etching on a countertop.

The website is low on specifics, but here it is, FWIW:

Here is a link that might be useful: slatescape

The website says the product has a water absorbancy of 20 - is that 20%? Wow - that is a very high absorbancy. It's heat limitations are 250 degrees - far less than granite. On one site I saw pictures of a fabricator frying a steak with a blowtorch on a granite slab. You couldn't do that with this product even if you wanted to. If you like the matte look I'd reconsider soapstone which has such terrific innert properties and is so very beautiful - especially the veined variety.

I investigated slatescape, but decided against it. I was concerned about its durability and it didn't come in the color I wanted ;-). They will send samples if you want to check it out.