🌙💙 Blue Synthetic Opal. 9x15mm Semicircle. Rhodium. The Necklace That Is Over the Moon in Blue Fire.

The semicircle is one of jewellery's most architectural and most considered forms — half of a circle, the flat edge giving the pendant a grounded, stable base while the curved edge rises above it in a graceful arc that is as elegant and as considered as a geometric shape can be. It is the shape of a horizon, of a rising sun, of the moon seen from a particular angle on a particular night — a shape that is as natural and as resonant as it is geometric, as organic as it is architectural. This rhodium plated sterling silver necklace carries that semicircle in its most magical, most luminous form: a 9mm x 15mm semicircle rendered in blue synthetic floating opal — the largest pendant in the blue synthetic opal series, its 15mm width giving the opal's own play-of-colour phenomenon the most surface area to work with, the blue fire of the synthetic opal moving across the full width of the semicircle in a continuous, sweeping play of blue and white light that is as dramatic and as alive as the opal phenomenon gets. The flat base of the semicircle sits at the neckline with a clean, architectural precision, the curved arc rising above it in a sweep of blue opal fire that is as over the moon as a pendant can be. The rhodium plating gives the setting a cool, mirror-bright finish. Lobster clasp. 16 inch with 2 inch extender. Pure .925 sterling silver beneath the rhodium.

The 9mm x 15mm size is the detail that makes this opal semicircle necklace the statement piece of the blue synthetic opal series — at 15mm wide, the semicircle has the most surface area of any pendant in the series, the blue opal fire sweeping across the full width of the pendant in a display of play-of-colour that is as dramatic and as commanding as the series gets. The floating opal effect — the play-of-colour appearing to float within the stone rather than on its surface — gives the semicircle a depth and a luminosity that is as enchanting up close as it is from across the room, the blue fire seeming to come from within the pendant rather than from its surface, as if the semicircle contains a small piece of the blue sky itself. The architectural semicircle form gives the pendant a contemporary, designer quality that the more conventional shapes in the series — the star, the moon, the cat — cannot replicate.

Wear it as your most architectural, most dramatic everyday piece — the blue opal semicircle necklace that is over the moon in blue fire at your neckline, the statement pendant of the blue synthetic opal series, a piece that is as bold and as luminous as a 15mm sweep of blue opal can be. Or gift it to someone who deserves the most dramatic, most architectural piece in the series: a lover of geometric jewellery, a collector of opal, anyone who is simply over the moon.

✨ Style & Wear

• 🌙 9mm x 15mm semicircle pendant — largest in the blue opal series, architectural and bold
• 💙 Blue synthetic floating opal — play-of-colour sweeps full 15mm width dramatically
• ☄️ Rhodium plating — cool mirror finish, complements the blue opal fire
• 🔗 16 inch + 2 inch extender — lobster clasp
• 🤍 Pure .925 sterling silver beneath rhodium plating
• 🎁 The statement opal gift — geometric jewellery lovers, opal collectors, anyone who is over the moon

💎 Quality & Certification

• ✅ Verified Authentication: Our core Brand Certifications and Assay Certificates are displayed on our Homepage. Please visit to view our full commitment to quality.
• 🏭 Premium Materials: We partner only with reliable professional suppliers — every piece meets our strict standards for genuine .925 Sterling Silver.

⚠️ Important: Size & Scale Disclaimer

• 📸 Macro Photography: Product images are taken with macro lenses to showcase detail — items may appear larger than actual size.
• 📐 Final Authority: Actual dimensions are strictly based on the physical measurements listed in the specifications table below. Please confirm before purchasing.

📐 Product Specifications

📦 Packaging

Your necklace arrives in a simple, understated box with a protective pouch — modest packaging that keeps the focus where it belongs: on the blue fire at your neckline.