Natural Tanzanite is trichroic and usually has a brown/orange, purple, and blue axis.  Usually the brown/orangish colored axis becomes intense purplish-blue when heat treated (almost all Tanzanite is heat-treated).  The blue and purple axis colors also may intensify greatly with heating. Untreated deep violet and blue crystals are possible but quite rare. Gems are usually cut on the deeper blue axis, but the purple axis also makes a terrific looking gem.
Tanzanite rough has continued to be very difficult to obtain.  We are pleased to be able to supply a small quantity of fine high-grade gem rough.  These are from native Tanzanian stake holders supporting local TZ citizens and local economy.

Sorry, all material has sold out. Given the current situation with this material we do not expect to restock it.
Treating:
As with most Tanzanite, the material should be treated in order to get the signature vivid Purplish-Blue color.  For best results, a clean gem should be cut from the material first and then treated between 700F to 1100F (371C - 590C) for about an hour (slowly ramping up the temperature, holding, and then slowly cooling all the way down to room temperature).  It is possible to treat the unfaceted rough first, however any inclusion/fracture even on the edge of the stone could possibly damage the entire piece as it is heated.  So it is recommended to first grind the rough stone into a nice clean chunk/pre-form before heating.