This glowing necklace has three Mexican fire opal cabochons, a large central one flanked by two smaller ones, each a "boulder" type with precious opal in matrix. Each is bezel-set in sterling silver with an open back.
The cabochons are oval; the central cab is about 15mm x 22mm x 7mm (0.6" x 0.9"), and the side cabs about 14mm x 17mm x 7mm (0.6 x 0.7"). The necklace is about 18" and fastens with a lobster clasp.