Carat【Carat: Weight】
Carat refers to the weight of a diamond and is expressed as “ct.” In general, larger diamonds are rarer and more valuable. When all other quality factors are equal, diamonds with higher carat weight tend to command higher prices.
Certain carat weights known as “Magic Sizes” are especially popular and tend to command higher prices.

Cut【Cut: Cut Quality】
Cut is the only one of the “4Cs” determined by human craftsmanship. Because the quality of the cut directly affects a diamond’s brilliance, it is considered one of the most important evaluation factors. Cut quality is assessed based on proportions, finish (polish), symmetry and the overall brilliance observed by the human eye. Diamonds are graded on a five-level scale: “Excellent”, “Very Good”, “Good”, “Fair” and “Poor.”

Clarity【Clarity: Purity & Transparency】
Clarity is the standard used to evaluate a diamond’s transparency. A skilled appraiser uses a 10x loupe to carefully inspect the size, position and number of inclusions (internal characteristics) and blemishes (surface flaws) that are naturally present in all diamonds. The fewer the characteristics and the more transparent and clear the stone is, the higher its rarity and value.

Color【Color: Color】
Diamonds are often thought of as completely colorless, but in reality they contain subtle variations in color. In general, the more colorless a diamond is, the higher its value. Diamond color is graded on a 23-level scale, ranging from the highest grade “D” to “Z” as yellow tones become more visible.

Even if you lose your grading report, it can usually be reissued through organisations such as the Central Gem Laboratory (CGL) or the GIA. However, reissuing a grading report may require additional fees of approximately SGD 20–100, as well as time and effort. If the diamond is set in a ring, there is also a risk of damage when removing the stone for inspection. Since grading reports themselves do not directly determine the value of a gemstone, we recommend choosing a trusted appraisal company with strong expertise and reliable evaluation standards.

The G.G. (Graduate Gemologist) qualification awarded by the GIA is internationally recognised as one of the most respected credentials in the field of gemology. Because of this expertise, our appraisers are able to provide accurate and reliable evaluations even without a grading report. If you are unsure about the appraisal price, you are welcome to start with an appraisal only. All appraisals at OTAKARAYA are completely free of charge.

It is possible to make a purchase even without a certificate of appraisal. At "Otakaraya," our appraisers, who have completed specialized training, will conduct the evaluation. You can rely on us with confidence.