This fantastic, impressive crystal is so glassy and clean that you can EASILY read right through the whole thing, and it is brilliantly lustrous and colorful to boot! It is one of the finest-quality crystals of ANY SIZE that I have seen. It is so clear and clean that it shows off its gemminess in even minimal lighting, no backlighting required at all. Heated tanzanite is a uniform blue in color, and loses the color-change so characteristic of the natrual stone. Natural tanzanite, for the most part, is dichroic purple and blue and at least weakly trichroic brown/red on the c axis. In practice, most crystals are more brown than red, and even then the red is usually very weak indeed. Not so with this magnificent crystal which shows not only royal blue and purple colors along its horizontal axes, but a true red-maroon hue along the c-axis when backlit from below or from the side, angling into the c-axis. In person, you can see that this is in the very top percentile of color saturation, and is probably one of the most trichroic crystal specimens to be had. Sometimes the color change from blue to purple is not so dramatic but here it is vibrant and shocking, as much so as the change to red along the c-axis which is visible even in room lighting. This crystal weighs 34 grams (170 carats) and is quite gemmy. The entirety of the interior is gemmy....indicating a HUGE value of gem rough inside, if it were to be butchered and the cut stones sold. Ex. Ed David Collection3.6 x 3.2 x 1.7 cm