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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. The stone is slightly included; 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 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 |
Slightly Included |
| 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: Slightly Included
- 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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