I would call it a soft by how it looks. The SG might tell you how some of the different companies at different times would have labelled it. But that's kind of irrelevant. Everything is a continuum. Nature never made two identical rocks. You'll never know how it acts until you try it. My guess if it behaves like most softs is that it cuts pretty quickly with pressure and burnishes if you lighten up. Effective grit range on the Shapton scale (I just mean compared to how Shaptons behave because that is what I know) about 800-1500 grit. The more porous and friable it is the faster it will be. The harder it is the the more fine a polish you can squeeze out of it. Porosity, friability, and hardness are linked in weird ways due to the other impurities that are in the stone besides quartz novaculite. And what layer of the earth it formed in will determine how metamorphosized it is. More cooking in the deep hot layers generally means a harder slower stone. But not always. Some of the hard ones will have sections with looser friable material or will be extra porous and still cut really fast. So we shouldn't really make generalizations. Try it out. I love soft arks for quick touch ups which is about 99% of my sharpening anyway. Try bringing the edge back on a well taken care of but well used knife that needs a pick me up. Just a few edge leading swipes after you clean up the stone a little and make sure it is pretty flat.
I have been thinking about the washita thread, and realized that sometimes, depending on particle size, novaculite has been used to make arrow heads.. In fact some of the material is sold in knapping circles.
So taking this to another level, I wondered if other types of arrow head material might be suitable for sharpening... I have access to a considerable quantity of a flint from Georgetown /Austin Texas area called Georgetown blue...
So I cut a piece and lapped the surface to smooth it out, and here is a picture...A super knapping material, and based on my limited ability to sharpen knives , also a very fine grade of polishing. Not really sharpening unless you have no life and want to spend hours on a single blade, but interesting, at least to me.
So no surprise, I can not load the picture. Imagine a grey/dark grey flat maybe 9x8".