Synthetic diamond "nanocrystalline" and "microcrystalline" diamond, respectively. Synthetic diamond is the hardest known material, where hardness is defined as resistance to indentation. The hardness of synthetic diamond depends on its purity, crystalline perfection and orientation: hardness is higher for flawless, pure crystals oriented to the <nowiki>[</nowiki>111<nowiki>]</nowiki> direction (along the longest diagonal of the cubic diamond lattice). Nanocrystalline diamond produced through CVD diamond growth can have a hardness ranging from 30% to 75% of that of single crystal diamond, and the hardness can be controlled for specific applications. Some synthetic single-crystal diamonds and HPHT nanocrystalline diamonds (see hyperdiamond) are harder than any known
Hope Diamond long been rumored to carry a curse, possibly due to agents trying to arouse interest in the stone. It was last reported to be insured for $250 million. The Hope Diamond, also known as Le Bijou du Roi ("the King's Jewel"), Le bleu de France ("France's Blue"), and the Tavernier Blue, is a large, , deep-blue diamond, and now housed in the National Gem and Mineral collection at the National Museum of Natural History in Washington, D.C. It is blue to the naked eye because of trace amounts of boron within its crystal structure, and exhibits a red phosphorescence under