• A blue boulder opal pendant set in 18k gold, featuring natural blue and white sapphires.
  • Back view of the 18k gold boulder opal pendant showing its hallmarks and ironstone matrix.
  • A blue boulder opal necklace being held by the chain against a black background.
  • A stylized angled view of the boulder opal and sapphire pendant on a black background.
  • Boulder opal pendant with a quarter and ruler for scale, measuring approximately 1.2 inches.
  • Blue boulder opal pendant displayed in a blue jewelry box against a black background.
  • A boulder opal and sapphire necklace resting on fingers, showing the deep blue hues.
  • Macro shot of the opal pendant resting on fingers, revealing blue and green flashes.
  • Angled macro shot of the boulder opal pendant, highlighting the vibrant sapphires.
  • Side view of the boulder opal and sapphire necklace, showing the opal’s natural texture.
  • Boulder opal necklace worn on a black t-shirt with a partially zipped sweatshirt.
  • Boulder opal pendant held outside in sunlight, showing blue and green flashes.
  • Macro close-up of the blue boulder opal necklace in natural sunlight.
  • Twisted angled view of the boulder opal necklace, revealing blue color play.
  • Angled macro view of the opposite side of the opal necklace, showing blue flashes.
  • Straight-on macro close-up of the opal pendant in sunlight, displaying blue fire.
  • Cover of the GGS gem report booklet and protective plastic sleeve against a black background.
  • Opened GGS gem report booklet showing opal necklace details with Japanese text.
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Kosei | 4.05ct Quilpie Boulder Opal & Sapphire Pendant in 18k Gold

Kosei | 4.05ct Quilpie Boulder Opal & Sapphire Pendant in 18k Gold

$1,880.00 USD
$1,880.00 USD
Sale Sold out

Meet Kosei,

A Modernist Boulder Opal & Sapphire Pendant in 18k Gold

Sleek, architectural, and undeniably unique—this handcrafted 18k yellow gold pendant presents a 4.05-carat Quilpie boulder opal, framed in a striking Japanese modernist design. The opal’s natural blue-green fire plays subtly across its earthy ironstone matrix, creating an organic contrast against the pendant’s structured gold frame.

Accented with 1.01 carats of natural sapphires and diamonds, the composition evokes an effortless balance of elegance and contemporary artistry. The open-frame slider setting, imported from Japan, allows light to pass through the design, adding an airy sophistication to the pendant’s geometric aesthetic.

This piece comes with a Gem Grading System Japan (GGS) certificate, verifying its natural boulder opal (translated from 天然ボルダーオパール) and sapphire (脇石は天然サファイアと認む) accents. The pendant measures 1.2” long and is accompanied by an 18” gold-plated sterling silver box chain.

Designed for those who appreciate artistic, one-of-a-kind jewelry, this pendant embodies a refined, gallery-worthy aesthetic—perfect for the modern collector.

 

More Information...

The Showcase Stones: Natural Boulder Opal, solid

  • carat weight: 4.05cts (inscribed on back of pendant)
  • origin: Quilpie, Queensland, Australia
  • shape: polished freeform
  • stone measurements (millimeters): 14.22mm x 8.57mm
  • stone measurements (inches): 0.6" x 0.33"
  • body tone: N4
  • brightness of color play: 2.5 of 5
  • color play description: blue/green only

The Accent Stones: Sapphire, natural

  • stone count: 6
  • total carat weight: 1.01cts (inscribed on back of pendant)
  • cut: faceted rounds
  • color: 4 stones are blue, 2 stones are white

The Setting: Open-Rectangle Bezel-Set Slider Pendant, chain included

  • pendant metal: 18k yellow gold, solid
  • chain metal: .925 sterling silver, gold plated
  • pendant length: 30.39mm (1.2")
  • pendant width: 13.29mm (0.5")
  • bail opening width: 1.77mm
  • pendant weight: 4.69 grams (not including chain)
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