This fantastic, impressive crystal is about 3.5 inches tall, nearly an inch thick, and brilliantly lustrous and colorful. It is one of the finest-preserved large crystals I have seen on the market, and is truly a "museum-grade" tanzanite because of the size, the natural color trichroism, and the gemminess which is easy to see with even minimal lighting. The termination is not only broad, but it is exquisitely formed and beveled as you can see! 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. It is very difficult to photograph, but the shots above gives you an idea of how rich these colors are (the purple and red hues, from side and long axes respectively). This crystal weighs 178 grams (890 carats) and is quite gemmy. It has surface veils as you can see, but the entirety of the interior is gemmy....indicating a HUGE value of gem rough inside, if it were to be butchered. 8.5 x 4 x 2 cm