"The Hope Diamond is a large (45.52 carat), deep blue diamond, currently housed in the Smithsonian Natural History Museum. The diamond is legendary for the curse it supposedly puts on whoever possesses it. The Hope Diamond appears a brilliant blue to the naked eye because of trace amounts of boron within the diamond. The Hope Diamond exhibits red phosphorescence under ultraviolet light and is classified as a Type IIb diamond."

Source: http://en.wikipedia.org/wiki/Hope_Diamond