Three people were arrested in Malaga for selling a gem for €600 having passed it off as a black diamond.
The gem was actually a spinel, a magnesium aluminium mineral, for which they had obtained a false authenticity certificate issued by an expert.
One of the detainees, aged 72, bought such gems online at a reduced price and took them to an expert who would provide him with a certificate for €35. It certified that they were diamonds.
He then sold one to another man, who, after realising it was not real, sold it on.
The gem expert claimed that he had made a mistake on the certificate, but police proved it is impossible to mistake one gem for another.