(IDEX Online) - Diamond billionaire Beny Steinmetz has lost an appeal against a conviction in a Swiss court for bribery, over an iron ore deal in Guinea.Three judges did, however, reduce the five-year prison sentence, handed down two years ago, to three years of which he must serve 18 months, according to a Reuters report.They also upheld the $52m fine, which was imposed at the same time, but acquitted him of a forgery charge.Steinmetz, 67, (pictured) a French and Israeli citizen whose personal fortune has been estimated at over $1bn, says he will appeal again, to Switzerland's highest court. In the meantime, he will spend time in prison.The original court hearing was told that Steinmetz and others paid $8.5m in a series of bribes to Mamadie Toure, widow of Guinea's former president Lansana Conte, to secure mining rights for the BSGR Group (Beny Steinmetz Group Resources), which is now in administration. Steinmetz (pictured) has always insisted he is innocent of any wrongdoing related to one of the world's biggest untapped deposits of iron ore. The deal struck in 2008 with one of Africa's poorest countries was described as winning the "jackpot". He paid around $160m for the exploration and mining rights, then sold half of them to Vale, the Brazilian multinational mining company, for $2.5bn. Steinmetz started out as a diamond trader in Antwerp, founded SDG (Steinmetz Diamonds Group) with his brother Daniel, became a major supplier and manufacturer, then diversified into real estate, mining, minerals, financing, oil and gas.