(IDEX Online) - Crypto boss Richard Heart has been accused of defrauding investors to buy The Enigma, the world's largest black natural color diamond - a 555.55-ct carbonado - for $4.3m.The SEC (Securities and Exchange Commission) in Washington, USA, yesterday (31 August) charged Richard Heart (aka Richard Schueler) and his crypto companies Hex, PulseChain, and PulseX, with conducting unregistered offerings of asset securities that raised over $1bn.It also charged Heart and PulseChain with fraud for misappropriating at least $12m to buy McLaren and Ferrari sports cars, four Rolex watches (together worth more than $3m) and The Enigma.The diamond was sold by Sotheby's in a single lot online auction without reserve in February. The auction house didn't name the buyer, but US tech entrepreneur Richard Heart, 42, tweeted his 180,000 followers that he'd bought it.He said he'd be paying for the gem with cryptocurrency and would re-name it the Hex.com diamond, after the blockchain platform he founded.Before the auction, Sotheby's said the 55-facet polished stone was "thought to have been created either from a meteoric impact or having actually emerged from a diamond-bearing asteroid that collided with Earth."Carbonado diamonds are 2.6 to 3.8 billion years old and extremely rare. They contain traces of nitrogen and hydrogen abundant in interstellar space, as well as osbornite, a mineral uniquely present in meteors.Pic shows The Enigma and Richard Heart