Dark Crystal Opal and Diamond Necklace 1x 15ct yellow gold tested as 15ct makers Marks T&S Possible late 19th to early 20th century set with dark Crystal opal4x oval and 2x drop shaped cabochon cut and 2x approx 0.03CT Old European cut diamonds and 2x approx 0.09CT Old European cut Diamonds. The total weight 7.8 grams.