18-karat White Gold Brooch-pendant With An 11.50-karat Black Opal And Diamonds

18-karat white gold brooch-pendant with an 11.50-karat black opal and diamonds

This 18-karat white gold brooch-pendant showcases a remarkable 11.50-karat natural black opal, cut into an oval cabochon with a domed back. It is surrounded by a pavé setting of brilliant-cut diamonds totaling 1.36 carats (Total Weight), creating a striking contrast between the sparkle of the diamonds and the depth of the opal.

The opal has a very dark ground tone, corresponding approximately to shades N2 to N3 on the black opal classification scale. This shade, close to black, gives the stone exceptional depth and beautifully highlights its play of colors.

The play-of-color pattern is of the Harlequin type, featuring broad, angular patches dominated by an intense blue ranging from electric blue to royal blue, punctuated by a few flashes of green along the edges of the colored patches. The intensity of the play of color is high, creating a spectacular contrast between the dark background and the iridescent reflections that shift depending on the stone’s orientation and the light.

The stone is highly translucent and shows no visible matrix, a quality particularly sought after in black opals of this category.

From a gemmological perspective, all of these characteristics—black body, blue-green dominance, a structure composed of broad bands, and the absence of matrix—are highly consistent with an Australian origin, most likely from the famous Lightning Ridge deposit in New South Wales. This deposit is world-renowned for producing the finest natural black opals. However, this origin remains a probable gemological attribution, in the absence of a certificate formally specifying the provenance.

The setting is composed of natural brilliant-cut diamonds, with a total weight of 1.36 carats (Total Weight). The diamonds are SI1 clarity and offer a beautiful brilliance that highlights the opal’s play of light without detracting from its presence.

The setting is crafted from 18-karat white gold and features an ingenious convertible jewelry design, allowing the piece to be worn as either a brooch or a pendant. This system, entirely original, is seamlessly integrated into the setting and offers great versatility.

The reverse side bears the original inscriptions “11.50,” corresponding to the opal’s weight, “1.36 TW” for the total weight of the diamonds (Total Weight), the “18K” hallmark, and the jeweler’s mark, attesting to the quality of craftsmanship.

The piece is in excellent condition.

Specifications

• Type: convertible brooch-pendant
• Metal: 18-karat white gold (750/1000)
• Main stone: natural black opal
• Opal weight: 11.50 carats
• Cut: oval cabochon with a domed back
• Background: N2-N3 (very dark)
• Pattern: Harlequin with large, angular patches
• Color play: predominantly electric blue to royal blue with flashes of green
• Probable origin: Lightning Ridge, New South Wales, Australia
• Diamonds: brilliant cut
• Total diamond weight: 1.36 carats (Total Weight)
• Diamond clarity: SI1
• Setting: Original convertible brooch/pendant system
• Pendant dimensions: 3.5 × 2 cm
• Weight: 9.8 g
• Markings: “11.50,” “1.36 TW,” “18K,” and jeweler’s hallmark
• Condition: excellent condition