Twinning in quartz, especially when well-formed in good crystals, is very beautiful. In my opinion, the most spectacular twinning in quartz is the Japan Law twin. This superb specimen exhibits sharp twinning and is transparent throughout, illustrating the habit about as well as you could ask - especially for a US specimen (they are more common from Brazil, or even old Japanese locales in this quality). For Montana in particular, this is just a buttkicker of a crystal. In addition, this pristine specimen is a doubly terminated floater complete even around the bottom where you'd normally expect a broken point; and with accenting inclusions of schorl near the base to give a little more visual interest to the piece without detracting the eye from the sharp symmetry. Hands down, one of the best examples of this material I have ever seen. Not surprising, since Marty almost certainly got it from his friend Dave Bunk, who also lives in Denver and happens to be the one who controls the production and marketing of these quartz twins.