The Hope Diamond! Museum of Natural History, Washington D.C. The weight of the Hope diamond for many years was reported to be 44.5 carats. In 1974 it was removed from its setting and found actually to weigh 45.52 carats. It is classified as a type IIb diamond, which are semiconductive and usually phosphoresce. The Hope diamond phosphoresces a strong red color, which will last for several seconds after exposure to short wave ultra-violet light. The diamond's blue coloration is attributed to t...