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
Klopman diamond Klopman Diamond also appeared in a "Screaming with Binky" short, in which Binky the Clown inadvertently caused a diamond cutter to shatter the Klopman Diamond into a small pile of dust. Mark Evanier claims credit for adding references to the Klopman diamond to "Garfield and Friends". As a nod to the old animated series, the more recent series "The Garfield Show" (also written by Evanier) has also included references to the Klopman Diamond, and a crystal referred to as the Klopman Crystal is made a plot device in the direct-to-video film "Garfield's Pet Force". There is also a reference to