Granite countertops have become quite popular lately. How is Granite typically fastened to base cabinets? Would it be suitable to use as a desktop, say with just four legs attached to it (not a full frame like a base cabinet)? Or would a structure like a base cabinet be needed with a wood frame on all sides underneath to support and fasten the granite?
I wouldn't just try to attach the legs directly to the granite (or really any material used as a work surface). The result will probably be quite unstable.
I'd build a free standing frame and then fix the worktop to that.
You can use a silicone adhesive to attach a slab of granite to use as a desktop. As long as the desk itself is sturdy and stable, it shouldn't be an issue. If the desk will be free standing (not attached to a wall), make sure it wont be too top heavy. You don't want your granite tipping over.