Buying a loose gemstone gives you independence, you get the freedom to make your own choice, your own jewelry design.
5.18 carat cushion-cut blue sapphire, sourced from Sri Lanka (Ceylon) and heat-treated, measuring 10.00 × 8.42 × 7.03 mm. Deep, saturated blue with lively light return across the mixed brilliant faceting — the color range known in the trade as Royal Blue. In our own assessment the stone has inclusions visible under 10×; inclusions are natural and fully disclosed, and the price reflects them. At 5.18 carats, a substantial center stone or collector piece. Accompanied by GIA Report #6237949095, a Sapphire Report confirming weight, dimensions, color, and treatment (geographic origin was not requested for this report).
Expert Opinion
Ahmed Shareek's Assessment
"This is one of the larger fine-color Ceylon blue sapphires we've carried this year — 5.18 carats of deep, saturated Royal Blue with strong light return through a well-cut cushion. Every claim on this page apart from clarity — which is our own assessment — is backed by its GIA report, including the heat treatment, so there's nothing left for the buyer to guess at."
Rarity Analysis
Fine blue sapphire over 5 carats, with strong saturation and clarity clean enough to remain fully transparent, is a small fraction of what reaches the market in any given year — most commercial blue sapphire sells well under 2 carats.
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Color: Deep, saturated "Royal Blue" is the most sought-after blue sapphire hue family; the majority of blue sapphire on the market runs lighter or grayer than this stone's intensity.
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Size: At 5.18 carats, this stone is well past the size at which fine sapphire becomes scarce — per-carat prices for sapphire generally rise, not fall, above 3–5 carats, because so few rough crystals yield a clean stone this large.
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Treatment: Heating is the standard, fully disclosed enhancement for the great majority of blue sapphire sold today; what's uncommon here isn't the treatment itself but combining that heated color with this size and clarity in one stone.
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Cut: This stone is fashioned as a Mixed Brilliant cushion — a brilliant-cut crown paired with a step-cut pavilion — a cutting approach aimed at balancing color depth with light return. Executing this on a large cushion outline without sacrificing weight is deliberate lapidary work, not standard commercial cutting.
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Documentation: A GIA report on a stone this size, confirming weight, dimensions, color, and treatment, gives buyers a level of independent verification that a large share of the sapphire market doesn't provide.
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Combined effect: Individually, heated Ceylon blue sapphire is common. A 5+ carat stone combining this saturation, this clarity, a well-executed cushion cut, and GIA documentation narrows the field to a small number of comparable stones available at any given time.
Buying Guidance
A few practical points to weigh before purchasing this specific stone:
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View it under more than one light source. This cushion's Mixed Brilliant faceting — a brilliant crown over a step-cut pavilion — is built to hold color under warm indoor lighting while still returning sparkle in daylight; a well-cut stone like this one should show even color face-up, without dark "windowing" at the corners.
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Plan the setting around a substantial center stone. At 10.00 × 8.42 × 7.03 mm and 5.18 carats, this stone needs a mount with prongs positioned to protect the cushion's corners, which are the most vulnerable point on any cushion-cut stone.
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Confirm treatment disclosure when comparison-shopping. This stone's GIA report states its heat treatment plainly — treat any comparable stone's listing that omits or is vague about treatment as a red flag, not an assumption of "untreated."
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Understand the heated-vs-unheated value tradeoff. Heating is a stable, industry-accepted enhancement that doesn't affect durability, and it's why this stone's Ceylon color and size are available at a materially lower per-carat price than a comparably sized unheated stone would command.
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Use the Try Before You Buy option if you would like to see the stone in hand before finalizing the purchase.
Learn More About This Gemstone
Gemstone Data — At a Glance
| Item # |
CG8312 |
| Carat Weight |
5.18 ct |
| Species / Variety |
Corundum — Blue Sapphire |
| Shape / Cut |
Rectangular Cushion, Mixed Brilliant (brilliant crown, step cut pavilion) |
| Dimensions |
10.00 × 8.42 × 7.03 mm |
| Color / Intensity |
Deep Blue — trade name "Royal Blue," intense saturation |
| Phenomenon |
None |
| Treatment |
Heated (disclosed on GIA report) |
| Origin |
Sri Lanka (Ceylon) |
| Clarity |
Inclusions visible under 10× — our own assessment; GIA colored-stone reports carry no clarity grade |
| Transparency |
Transparent |
| Hardness |
9 (Mohs) |
| Certification |
GIA Report #6237949095 |
Features
- SKU: CG8312
- Carat Weight: 5.18 carats
- Variety: Blue Sapphire
- Shape: Rectangular Cushion
- Cutting Style: Mixed Brilliant (brilliant crown, step cut pavilion)
- Dimensions: 10.00 × 8.42 × 7.03 mm
- Gem Type: Natural Blue Sapphire
- Origin: Sri Lanka (Ceylon)
- Treatment: Heated
- Color: Deep Blue (Royal Blue)
- Transparency: Transparent
- Clarity: Inclusions visible under 10× — our own assessment, not a GIA grade
- Certification: GIA Report #6237949095
- Hardness: 9 on the Mohs scale
Care
- Clean with lukewarm water and mild soap using a soft brush
- Store separately to avoid surface contact
- Remove before heavy physical activity
- Avoid ultrasonic or steam cleaners
One of a Kind
This is a single natural gemstone, not a manufactured or lab-created replica — no two sapphires form with identical color, inclusions, and internal character. Once this stone sells, it's gone; there is no duplicate. What you see documented on the GIA report is the exact, individual stone you receive.
What's included with this Blue Sapphire
- GIA Report #6237949095
- Gemstone packed in a gem sleeve
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