A very clear quartz crystal. In Madagascar I can search through burlap sack after burlap sack full of quartz crystals, and not find a single piece as clear or sharp as these Arkansas examples.
I honestly don't understand the pricing of these things... sometimes you'll see one the same size for $100, sometimes it's cheaper.... sometimes it's some exorbitant amount and they are priced by the gram.... whatever the case, I like my price.