The 29-year-old pleaded not guilty to one charge of conspiracy to defraud investors, with the knowledge that the coloured diamonds did not represent a legitimate investment opportunity.
There were around 50 victims involved in the alleged fraud, a previous hearing heard.
Bloor, who wore a navy blue blazer and trousers at Southwark Crown Court, spoke only to confirm his name and date of birth.
The former reality star, from Essex, joined the cast of the popular ITV2 show in 2013 for three years, and became romantically involved with several cast members including Lauren Pope.
In 2016, he took part in the 18th series of Celebrity Big Brother, where he was the fifth housemate to be evicted.
The conspiracy is claimed to have taken place between 17 May 2013 and 19 June 2014.
Bloor sat in the dock with his co-defendants Joseph Jordan, 26, from Hertfordshire, George Walters, 27, from Kent, Max Potter, 22, from Middlesex, and Nathan Wilson, 25, from Essex – all of whom pleaded not guilty to conspiracy to defraud.
Another co-defendant, 25-year-old Simon Akbari, from Loughton, Essex, did not enter a plea to the same charge.
Danny Chappell, 52, of Bexleyheath, Kent, denied a charge of seeking money for completing renovation works which had not been undertaken in 2014.
The amount of money lost was allegedly “in excess” of £3m.
The trial has been adjourned to the week of 1 September 2020.