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Reference Values of Gems
Database updated: 26 September 2017
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Interactive online gem appraisal model

To provide you with the most accurate online appraisal possible, we have created a sophisticated mathematical model. Each gemstone appraisal is based on a complex statistical analysis of current online sales prices for natural colored gems. The algorithm takes into account the specific factors influencing a gem's price, such as; weight, color, clarity, cut and shape. We collect statistical market data by examining hundreds of lots from different gem sellers every month. Please be aware that the pricing model parameters (value factors) are generally updated monthly, so any estimated value will vary slightly over time.

How we collect data

We add new online shops to our tracking list every month so our online gemstone resources are continuously growing. We thoroughly check and categorize each online resource before we assign it a value on our dependency index. To optimize accuracy we make sure that only market-balanced offers are entered into the database. All specimens with highly irregular prices are rejected and therefore have no impact upon statistical coefficients.

Gemstone dealers are more than welcome to contact us and be included in our tracking list free of charge.

Valuation model

Generally speaking, the value of any natural gemstone may be approximated by using the following formula:

Val = (L0 + L1 * W) * W * C1 * C2 * C3 * C4

Where

L0, L1 - linear price per carat trend for selected gemstone variety,

W - weight,

C1 - color coefficient,

C2 - clarity coefficient,

C3 - quality of cut coefficient.

C4 - shape coefficient (for some gemstone types).

The values of relevant coefficients are derived by the 'Least Square Method'. Currently our statistical database contains over 70000 records, and as a rule we upload new records to our database and recalculate the coefficients on a monthly basis.


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