Hope Diamond - Physical Properties

Physical Properties

• Weight. In December 1988, the Gemological Institute of America's Gem Trade Lab determined that the diamond weighed 45.52 carats (9.1 g).

• Size and shape. The diamond has been compared in size and shape to a pigeon egg, walnut, a "good sized horse chestnut" which is "pear shaped." The dimensions in terms of length, width, and depth are 25.60mm × 21.78mm × 12.00mm (1in × 7/8in × 15/32in).

• Color. It has been described as being "fancy dark greyish-blue" as well as being "dark blue in color" or having a "steely-blue" color. As colored diamond expert Stephen Hofer points out, blue diamonds similar to the Hope can be shown by colorimetric measurements to be grayer (lower in saturation) than blue sapphires. In 1996, the Gemological Institute of America's Gem Trade Lab examined the diamond and, using their proprietary scale, graded it fancy deep grayish blue. Visually, the gray modifier (mask) is so dark (indigo) that it produces an "inky" effect appearing almost blackish-blue in incandescent light. Current photographs of the Hope Diamond use high-intensity light sources that tend to maximize the brilliance of gemstones. In popular literature, many superlatives have been used to describe the Hope Diamond as a "superfine deep blue", often comparing it to the color of a fine sapphire "blue of the most beautiful blue sapphire" (Deulafait), and describing its color as "a sapphire blue". Tavernier had described it as a "beautiful violet".

• Emits a red glow. The stone exhibits an unusually intense and strongly colored type of luminescence: after exposure to short-wave ultraviolet light, the diamond produces a brilliant red phosphorescence ('glow-in-the-dark' effect) that persists for some time after the light source has been switched off, and this strange quality may have helped fuel "its reputation of being cursed." The red glow helps scientists "fingerprint" blue diamonds, allowing them to "tell the real ones from the artificial." The red glow indicates that a different mix of boron and nitrogen is within the stone, according to Jeffrey Post in the journal Geology.

People typically think of the Hope Diamond as a historic gem, but this study underscores its importance as a rare scientific specimen that can provide vital insights into our knowledge of diamonds and how they are formed in the earth. —Dr. Jeffrey Post, Smithsonian curator, 2008

• Clarity. The clarity was determined to be VS1, with whitish graining present.

• Cut. The cut was described as being "cushion antique brilliant with a faceted girdle and extra facets on the pavilion."

• Chemical composition. In 2010, the diamond was removed from its setting in order to measure its chemical composition; after boring a hole one nanometre (four-billionths of an inch) deep, preliminary results detected the presence of boron, hydrogen and possibly nitrogen; the boron concentration varies from zero to eight parts per million. According to Smithsonian curator Dr. Jeffrey Post, the boron may be responsible for causing the blue color of the stones after tests using infrared light measured a spectrum of the gems.

• Touch and feel. When Associated Press reporter Ron Edmonds was allowed by Smithsonian officials to hold the gem in his hand in 2003, he wrote that the first thought that had come into his mind was: "Wow". It was described as "cool to the touch." He wrote:

You cradle the 45.5-carat stone—about the size of a walnut and heavier than its translucence makes it appear—turning it from side to side as the light flashes from its facets, knowing it's the hardest natural material yet fearful of dropping it. —Associated Press reporter Ron Edmonds in 2003

• Hardness. Diamonds in general, including the Hope Diamond, are considered to be the hardest natural mineral on the Earth, but because of diamond's crystalline structure, there are weak planes in the bonds which permit jewelers to slice a diamond and, in so doing, to cause it to sparkle by refracting light in different ways. There were reports in October 2011 that researchers at Stanford University have created an even harder man-made substance called an amorphous diamond by using ultrahigh pressure conditions to create a non-crystalline structure which lacks the weak planes.