provenance is only one aspect of value. sure, tanzanite is rare, and probably getting rarer daily... whether it is treated or not is pretty much academic, as many colored stones are routinely heat-treated... some gem organizations don't even consider cooking a stone to be "treatment", yeah, that's a bit odd. IF you see a tanzanite that is a deep blue with a purple fire inside it and is over 1ct, you have a special stone, and if someone is pricing it really high, don't be surprised. If you see a ring set with tiny pale lavender stones and they tell you its tanzanite, well, no... those shouldn't be marked very expensive. YES, tanzanite is VERY SOFT for a gemstone, and while usually a 7 is the MINIMUM you would put in a ring, a large expensive tanzanite of good color in a pendant is a lovely precious thing.