A jeweler with a diamond tester would be very easy. I don't know if a diamond will even fracture properly when trying to form a arrowhead. I don't know if it results are a concoidal fracture like glass, obsidian, opal, flint, and chrystaline quartz.
But, just because it is the hardest rock, and or substance, on the earth, doesn't mean it can't break--it does!
I have found a fruit jar bottom, turned pink by the sun, shaped into a scraper. Probably not as durable as rock, but still.....