Olivier Martinez reportedly took an ''alchemy test'' to help with the design of Halle Berry's engagement ring.

The 46-year-old actor was apparently ordered to take the 500-year-old mystical quiz by Paris-based jeweller Robert Mazlo, who he turned to to create the yellow gold and emerald ring.

According to a source, Olivier had to answer seven questions about his 'Dark Tides' co-star's favourite shapes, colours, numbers and signs, which Robert ''decoded'' and used to perfect The Ring.

The insider told US Weekly: ''Olivier was absolutely delighted with the result.''

It is not yet known when or where he and 45-year-old Halle - who has daughter Nahla, three, with ex-boyfriend Gabriel Aubry and was previously married to baseball player David Justice and singer Eric Benet - will tie the knot.

However, his home county of France is said to be in the frame.

The source added: ''[Plans are] not yet finalised, [but there's a] very good chance it would be in Paris. It will be first time round for Olivier ... he would love it to be in his home city - the city he knows and loves.''