text: An American Art Nouveau 18 karat gold and platinum brooch/pendant with black opal, diamonds and enamel by Marcus Co. The brooch/pendant has a center cabochon opal and 76 old mine-cut diamonds with an approximate total weight of carats. Opal Jewelry, Jewelry Art, Antique Jewelry, Vintage Jewelry, Fine Jewelry, Fashion Jewelry, Jewelry Design, Vintage Brooches, Jewellery