Transparent Diamond Grading & Appraisal.
Know Exactly What You Own. No Hidden Costs.
Book a ConsultationKnow Exactly What You Own
A diamond's value is determined by four characteristics, and small differences in any one of them can have a significant impact on price. Professional grading ensures you know exactly what you have, or exactly what you are buying.
At Jay Gems, our grading uses GIA methodology. We grade and appraise diamonds for private clients, jewellers, dealers and investors, giving you clear, documented and defensible assessments for buying, selling or insuring your stones.
Our team has assessed thousands of stones across a wide range of shapes, sizes and qualities, giving us the depth of experience to provide services reliable and accurate assessments.
Understanding the 4Cs
◆The 4Cs are the universal language of diamond quality, developed by the GIA and used by every professional grader worldwide.
The most important factor. Determines how brilliantly a diamond reflects and refracts light. A well-cut stone will outshine a higher-colour or higher-clarity stone with a poor cut.
Graded D (colourless) through to Z (light yellow). The less colour a diamond shows, the rarer and more valuable it is. Differences between grades are subtle but can significantly affect price.
Measures internal inclusions and surface blemishes. Graded from Flawless through to Included. Most inclusions are invisible to the naked eye -- the grade tells you where the stone sits on the scale.
The weight of the diamond measured in carats. Price increases exponentially with carat weight, not linearly -- a 2ct diamond of equal quality is worth significantly more than two 1ct stones.
Grading & Appraisal Services
A comprehensive assessment of a loose diamond covering all 4Cs, fluorescence, measurements and finish grades. Clear, documented and reliable -- essential for buying, selling or trading with confidence.
A professional valuation of finished jewellery. Covers the stones, metal, craftsmanship and current market value. Required for insurance, estate planning and resale -- we make the process straightforward.
Thinking about buying a diamond? Our experts assess the stone and give you an honest view on whether the asking price reflects true quality. We are here to protect you, not to sell you anything.
We verify GIA certificates against the physical stone, confirming the certificate matches the diamond being presented. Particularly important for pre-owned diamond purchases where authenticity matters.
Diamond Grading FAQs
Know the True Value of Your Diamond.
Send us a message to arrange a grading or appraisal assessment. In person in Bangkok or by secure international shipping.
Book a Consultation