In 1970, Louis Glick acquired the 890 carat (178 g) Incomparable Diamond, at that time the world's fourth largest rough diamond.^[1] The carat is a unit of mass used for gems, and equals 200 milligrams or 3. ... This article is about the gemstone. ...

Alternate sources claim that this stone was only discovered in the early 1980s in the town of Mbuji Mayi in the Democratic Republic of Congo, by a young girl playing outside her uncle's house, where rubble from a nearby diamond mine had been dumped.^[2]

The stone was cut by a team led by Marvin Samuels, who co-owned the stone along with Donald Zale of Zales Jewellers and Louis Glick. In November 1984 the finished stones were put on display: a single golden diamond of 407.48 carats (81.496 g) in a 'triolette' shape, and fourteen additional gems. Notably, the satellite stones cut from the Incomparable varied greatly in colour, from near-colourless to rich yellow-brown. Zale Corporation (NYSE: ZLC) is the largest specialty retailer of fine jewelry in North America, operating over 2,300 retail locations (which includes both kiosks and stores) throughout the United States, Canada, and Puerto Rico. ... In order to best utilize a diamond gemstones superlative material properties, a number of different diamond cuts have been developed. ...

The largest of these stones still bears the name 'Incomparable Diamond', and was graded by the GIA as internally flawless in 1988.^[3] The Gemological Institute of America, or GIA, is a non-profit institute dedicated to research and education in the field of gemology. ... Diamond clarity is a quality of diamonds relating to the existence and visual appearance of internal defects of a diamond called inclusions, and surface defects called blemishes. ...

Unusually, the Incomparable Diamond made an appearance on eBay in November 2002, though it remained unsold with a reserve of £15 million pounds sterling.^[4]

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