This is a very red fire opal necklace. The opal is transparent and large, of a quality that is rarely found. The bail is also beautiful, with diamonds. I purchased it at a mineral show. Stamped K18. Total length: 20mm The stone is approximately 12mm x 10mm in size. There is a carat marking, but it is too small to read. Please estimate from the size. Necklace top only.