天然グリーンダイヤモンド ルース

A loose natural green diamond is an unmounted, unset stone whose green colour has been formed entirely by natural geological processes — specifically, exposure to naturally occurring radiation over millions to hundreds of millions of years as the diamond migrated towards the earth's surface. It has not been placed into any ring, pendant, or jewellery setting, allowing you to inspect the stone from every angle, verify its characteristics against the grading certificate, and make a fully informed purchase decision before committing to a design.

This is the preferred route for buyers who demand complete transparency over quality, those building a fine jewellery collection from the stone up, and investors seeking a certified, independently valued tangible asset. Explore our finished pieces in the green diamond ring collection, or contact us to discuss a bespoke commission.

This is the single most critical question to ask when purchasing any green diamond — loose or set — and the answer has a profound impact on value.

Natural green diamonds acquire their colour through millions of years of exposure to naturally occurring radiation within the earth. The GIA confirms this origin through rigorous spectroscopic analysis and states "Natural Color" explicitly on the grading report. These stones are extraordinarily rare and command significant premiums in the market.

Treated green diamonds are colourless or near-colourless diamonds subjected to artificial irradiation or HPHT (High Pressure High Temperature) processing in a laboratory environment to induce a green colour. They can be visually indistinguishable from natural stones to the naked eye, but their market value is a fraction of that of a naturally coloured diamond. The GIA report for a treated stone will clearly state "Artificially Irradiated" or equivalent language.

Every loose green diamond in our collection has been independently certified as Natural Color by the GIA or CGL. We never represent treated stones as natural — the certificate accompanying every purchase provides unambiguous confirmation of origin.

The rarity of natural green diamonds as loose certified stones is the result of several compounding factors unique to this colour category:

Surface-only colouration in most stones — In the majority of natural green diamonds, the radiation-induced colour exists only in a thin layer near the surface of the rough crystal. When the stone is cut and polished, the lapidary must work with extraordinary precision to preserve this colour — and even then, a significant portion of the colour depth can be lost. Many rough green diamonds never yield a commercially viable faceted stone retaining strong colour.

Deep-body colour is extraordinarily scarce — Stones in which the green colour permeates the entire crystal — so-called deep-body or body-colour green diamonds — are among the rarest objects in the natural world. When such stones appear at major auction houses, they routinely set price-per-carat records.

Rigorous natural colour verification — Because green can also be induced artificially, the GIA applies its most stringent testing protocols to green diamonds. Only a small proportion of submitted stones receive the coveted "Natural Color" designation.

Geographically restricted sources — Significant natural green diamonds have been recorded primarily from Brazil, the Democratic Republic of Congo, India, and Zimbabwe — a limited and irregular supply chain with no major dedicated green diamond mine.

Loose green diamonds are graded by the GIA on the standard fancy colour intensity scale:

Faint Green → Very Light Green → Light Green → Fancy Light Green → Fancy Green → Fancy Intense Green → Fancy Vivid Green / Fancy Deep Green

The deeper and more saturated the colour, the rarer and more valuable the stone. Alongside intensity, the GIA also grades the colour modifier (hue), which significantly affects market value:

Pure Green — The rarest and most valuable hue. Stones with no secondary modifier command the highest premiums globally.

Bluish Green — Highly prized for its resemblance to fine emerald. Strong collector and investor demand worldwide.

Yellowish Green — More commonly encountered; generally the most accessible entry point into natural green diamonds.

Greyish Green / Brownish Green — Lower value modifiers, though each stone retains the beauty and rarity of a natural fancy colour diamond.

For loose stones specifically, it is also worth noting whether the colour is classified as Even, Uneven, or Patchy in distribution — even colour throughout the stone commands a substantial premium over uneven or surface-concentrated colour.

For a stone as rare and nuanced as a natural green diamond, buying loose offers particularly compelling advantages:

Complete visual inspection — You can examine the entire stone including the pavilion, girdle, and culet — areas hidden once the stone is set. For green diamonds, this allows you to personally assess the depth, distribution, and consistency of the colour throughout the crystal, not just at the surface.

Direct certificate verification — With a loose stone in hand, you can cross-reference every detail of the GIA or CGL report against the physical stone, including the critical "Natural Color" designation.

Superior value for budget — Pre-set jewellery incorporates labour, design, setting, and brand margins on top of the stone cost. A loose diamond allows you to allocate more of your budget directly to the quality of the stone itself.

Total design freedom — Select your own setting style, metal (PT950 platinum, 18K yellow gold, rose gold, white gold), and overall design to create a piece that perfectly expresses the stone's unique character.

Cleaner investment asset — A certified loose diamond is independently appraised, insured, and resold as a discrete asset. The value of the stone and the setting are not conflated, making it a more straightforward investment vehicle than a mounted piece.

Yes. Every loose green diamond we offer is accompanied by an official grading report from the GIA (Gemological Institute of America) or CGL (Central Gem Laboratory) — the two most authoritative gemological laboratories in the world for fancy colour diamond certification.

The certificate documents the stone's colour grade, colour origin (Natural or Treated — the most critical field for green diamonds), colour modifier, colour distribution, clarity grade, carat weight, cut, polish, symmetry, and fluorescence.

We strongly recommend every buyer review the grading report in full before purchasing. Our specialists are always available to walk you through each field on the certificate and explain what it means for the stone's quality, rarity, and long-term value. For green diamonds in particular, never purchase without a GIA or CGL report confirming Natural Color origin.

Certified loose natural green diamonds — particularly those graded Fancy Intense or Fancy Vivid with Pure Green or Bluish Green modifiers — are widely considered among the most investment-compelling gemstones available anywhere in the world. Key factors underpinning their investment case:

Proven auction track record — The Aurora Green (5.03ct Fancy Vivid Green, Christie's 2016: $16.8 million / $3.3 million per carat) and the Dragon Vivid Green (5.04ct, Sotheby's 2023: $8.7 million) stand as benchmarks for the category's value trajectory at the highest level.

Absolute supply ceiling — Unlike most commodities, the supply of investment-grade natural green diamonds cannot be increased. There is no active large-scale green diamond mine, and the geological conditions required to produce them cannot be replicated or accelerated.

Rising global awareness — As collector and investor knowledge of green diamonds deepens — particularly across Asia and the Middle East — demand is intensifying while supply remains structurally fixed.

Loose format advantages for investors — A certified loose stone is easier to value independently, insure accurately, transport privately, and liquidate internationally than a mounted piece. It is a purer expression of the underlying asset.

Inflation and currency hedge — Rare physical assets with intrinsic scarcity have historically demonstrated resilience during periods of currency devaluation and financial market volatility.

We recommend consulting a qualified financial adviser alongside any gemstone investment decision. The fundamental supply-demand dynamics for natural green diamonds, however, are uniquely compelling.

Cut selection is particularly consequential for green diamonds because the cutting process directly determines how much of the surface-concentrated colour is preserved in the finished stone. Skilled lapidarists working with green rough prioritise colour retention above all else, which is why certain shapes predominate in the market:

Cushion Cut — The most widely favoured cut for green diamonds. Its deeper pavilion and rounded corners allow the lapidary to preserve more of the coloured surface layer while delivering a soft, romantic brilliance.

Radiant Cut — Excellent colour retention combined with exceptional brilliance. A popular choice for buyers who want the vibrancy of a fancy cut with near-round light return.

Oval Cut — Balances colour depth with elegant elongation. The oval's curved outline minimises colour loss at the edges and flatters the stone on the finger.

Pear Cut — Creates a distinctive, romantic silhouette while preserving colour effectively in the rounded body of the stone.

Round Brilliant Cut — Maximises light return and sparkle but can sacrifice more colour depth than step or mixed cuts. Best suited to stones with deep-body or even colour distribution.

The optimal cut for any given rough stone depends on its specific colour distribution and depth. Our specialists can advise on the best cut for your chosen stone — contact us or visit our showroom to discuss in person.

Absolutely — and a loose natural green diamond makes one of the most extraordinary foundations imaginable for a bespoke engagement ring or special commission. Once you have selected your stone, our team will guide you through every stage of the design process: setting style, metal choice (PT950 platinum, 18K yellow gold, rose gold, white gold), side stone selection if desired, and all finishing details.

Popular setting directions for green diamonds include:

Yellow gold prong solitaire — Classic, warm, and timeless. The gold enhances the green's natural warmth.
Platinum halo — White metal creates a sharp contrast that intensifies the green colour, with accent diamonds amplifying the centre stone's presence.
Rose gold bezel or pavé — Modern and romantic, with a soft contrast that suits lighter Fancy Light Green stones beautifully.

Whether you arrive with a clear brief or simply a love of the stone, we will bring your vision to life. Contact us or visit our private Tokyo showroom to begin. You can also browse our ready-to-wear green diamond ring collection for design inspiration.

Yes — and for natural green diamonds, we consider an in-person viewing not just recommended but essential. No photograph, video, or screen calibration can accurately render the colour of a natural green diamond. The hue shifts dramatically between natural daylight, fluorescent light, and incandescent light — and this interplay is a fundamental part of what makes these stones so captivating and unique.

At our private Tokyo showroom, one of our specialists will present the stone under multiple light sources, explain the grading report in full detail, and give you the time and space to form a genuine connection with the stone — with absolutely no pressure. For a purchase of this significance and rarity, we believe the in-person experience is irreplaceable.

Viewings are by private appointment only. Please use our contact form to reserve your session.

Yes. Weiss offers a money-back guarantee on our loose diamonds and jewellery. Acquiring a certified natural green diamond is one of the most significant gemstone purchases a collector or investor can make, and we are fully committed to ensuring your confidence at every stage — from first enquiry through to long after delivery. Full terms and conditions are available on our Money-Back Guarantee page. If you have any questions before proceeding, please do not hesitate to get in touch — we are here to help you make the right decision.