Estate 6.17 carat tanzanite and diamond ring. This 18 karat white gold ring has one rectangular tanzanite at 6.17 carats with AAA color, accented by 120 diamonds at 0.93 carat total weight having SI2 clarity and G color. The band is in a unique twist design. This tanzanite diamond ring is appraised at $14,500. The tanzanite ring is a size 6.5.