Gemological or economic evaluation of gemstones?

Gemological or economic evaluation of gemstones?

Many people turn to us for an evaluation of the gems in their possession, but we must specify that the purpose of our laboratory is not to provide economic assessments on the gem material, but to proceed with the identification and definition of the physical characteristics.

Let’s start by explaining what we mean by identification.
A gem is a mineral that not only requires a visual analysis to be identified, but also an analysis of its optical and physical properties performed with specific instruments, within a laboratory.
In the scientific nomenclature, the mineral is defined by identifying the mineralogical species to which it belongs and the variety (in a mineralogical species there may in fact be several varieties).
Here are some examples of gems that belong to the same mineralogical species, but represent different varieties of the same because of the different chromophores, chemical elements that characterize the color of the crystal.
ES:
Green gem: Mineral species Beryl (aluminum silicate and beryllium, Be3Al2 [Si6O8]), Emerald variety (chromophore: Chromium)
Blue gem: Mineral species Beryl (aluminum silicate and beryllium, Be3Al2 [Si6O8]), Aquamarine variety (chromophore: Iron)
The color, however, is not uniquely linked to a single variety of a single mineralogical species: a green gem can be an emerald, but tourmalines, garnets or peridots, etc. also exist in this color.
The identification work on the basis of the physical and optical characteristics of the mineral is up to a professional gemologist.
Once the material has been identified, the gemologist’s task is to understand whether it has a natural or synthetic origin (ie it was artificially produced in the laboratory).
In fact, we keep in mind that a natural and a synthetic gem have the same chemical formula and the same physical properties. For example, a synthetic emerald and a natural emerald have the same chemical formula (Be3Al2 [Si6O8]), but they can be distinguished by the different internal growth characteristics and thanks to the presence of typical inclusions, which can only be found under the microscope.

Once the gem has been identified and its natural origin defined … how do we know how much it is worth?

The answer is not that simple and it is not gemological laboratories like ours that can give you this information. The professional figure you should contact is that of the Appraiser who in Italy is often delegated to experts who work for auction houses, insurance companies or courts. The Appraisers carry out an evaluation of the gem and arrive at an economic quotation; to do this they start from a gemological certificate.
To obtain from them an exhaustive evaluation (and therefore a correct quotation) we should present them with a gemological certificate as complete as possible, which also specifies any treatments to which the gem has been subjected.
In fact, there are very invasive treatments that involve huge differences in the price of a gem. To give an example of all, in the case of Rubies, simple heating is commonly accepted, while the presence of fillings of the cracks with lead glass or external coloring through thermal diffusion are considered invasive as they modify the original quality of the gem. Such artificially embellished gems over the years can be prone to deterioration and their cost should be much lower than totally natural gems.
After identifying a gem, verifying its naturalness and explaining any treatments, numerous parameters still need to be defined in order to be able to attribute a price to it.
In fact, it is necessary to deal with a multi-criterion and weight assessment.
One of the most easily priced gems is the diamond. By now the 4Cs that define the quality of a diamond have been widely made known and sponsored by some well-known jewelry brands.

The 4Cs are nothing more than the initials (in English) of the 4 fundamental parameters for the definition and evaluation of a diamond: color, cut, clarity and carat (color, cut, purity and carat).
If you have a gemological certificate, your diamond can be easily listed on the market using one of the most used and recognized price lists: the Rapaport. This is a wholesale price list (prices excluding VAT) in dollars that is periodically updated on the basis of international market trends. This price list cannot be disclosed and can be purchased on the website: https://rapaport.com/
It consists of a simple table showing the prices per carat (multiplied by the weight of our diamond) based on the color and purity of our stone.

It is quite another story if a colored stone is to be quoted: in fact, a greater number of aspects will have to be considered. The so-called “4C” (color, cut, purity and carat) are evaluated in a more complex way and to these are added other parameters characterizing the quality and therefore the economic value of the gem.

Let’s see what are the parameters to consider when evaluating a colored gem:

Color: it is one of the most important characteristics and must be evaluated in its components: hue, saturation and hue. The higher the saturation, the higher the quote. As for the tonality, the middle terms are generally more popular. The color is variety specific and often an element of rarity.
Purity: important parameter for commonly clear stones such as quartz and less important in stones commonly more included for their genesis such as emeralds. A low purity can be considered detrimental to the beauty of the gem and therefore to its value
Cut: it is not considered as important as for diamonds, as colored stones almost never have a pre-established number of facets and cut proportions. There are elements that can be evaluated (window effects, extinction zones, cleaning) but parameters that are difficult to measure and often questionable remain.
Some characteristics of the cut can be mistakenly evaluated as negative. For example, for rubies, the apex of the pavilion may not be centered; this characteristic of asymmetry, however, is often desired by the cutter who follows the optical axis of the mineral to enhance its color to the maximum.
Carats: the valuation of the price per carat can remain almost constant for some gems, such as citrines or amethysts, while it increases exponentially as for emeralds, rubies etc.
Origin: for market reasons some areas of origin of the gems involve higher prices than others, because they are more renowned or because the production of some mines is on the verge of extinction and the price of the material suffers the consequences.
Treatments: The more or less invasive beautification treatments that the gem has undergone can drastically affect its price.
The quality of a colored gem depends on all these parameters and their weighted evaluation, combined with a good dose of experience and knowledge of the gem material, translate into an economic estimate.
Ultimately this price must be related to the local market and therefore consider supply and demand. For example, for cultural reasons, some gems are generally more in demand in the East than in the West, or simply the demand can change for fashion reasons.
The Luxedo gemological laboratory works on behalf of third parties for the drafting of gemological certificates according to the UNI standards defined by the Italian state, which provides for the identification and definition of the gemological characteristics of the stone. We do not, however, issue economic quotations.
Our commercial part that is our On-line store  and the Shop located in Riccione offers only high quality natural gems, coming from all parts of the world and imported directly from the source. The stones are all pre-analyzed by our gemologists and the price definition takes into account all the evaluation parameters described in this article.

 

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