It is a ceramic, by the very nature of that it must be brittle. Now you have to have a perspective what brittle actually means. It means you don't get much yielding before failure. The stuff is undoubtedly quite hard and likely takes a beating to get a crack started, but cracks will go once they start. The thing about composites though, is that they do a great job of allowing different materials to cover the properties of others. I suppose it is possible that the substance is transition stabilized, which can reduce fracture propagation, but I couldn't find any articles back this up. for the moment I'm assuming it's a composite.
Now difficult to scratch is in no way counter to being brittle. Generally in fact, things that are very hard (which means difficult to scratch) are brittle.
buzzard