Nowadays the term of "gemstone" is regulated by Federal Law No. 41-FZ of March 26, 1998 (as amended on July 3, 2016) "On Precious Metals and Gemstones". The law reads: "gemstones are a mineral crystal such as natural diamond, emerald, ruby, sapphire and alexandrite, or organic such as natural pearls in raw (natural) and treated form, or mineraloid such as unique amber formations are therefore considered to be gemstones as well, and equated in the order established by the Government of the Russian Federation. Materials of an artificial origin with the properties of gemstones are not defined as gemstones".
For the first time the term "gemstone" was used in the legislation of Russia regarding the adoption of the Resolution of the Supreme Economic Council of the RSFSR of February 22, 1918 "On the main gold committee and on the order of application of the SEC resolution on gold and platinum", where "diamonds and cut diamonds" and "other gemstones".
In the classification of jewelry stones, the term "gemstones" is introduced by Sobolevsky V.I. in 1971, associating them with the concept of "gems".
The market price of any product is defined by the ratio of demand and supply. However, with respect to synthetic stones one should take into account such factor as the production cost and its profitability.
To grow a complete analog of natural stone in laboratory now is much more costly than to mine a natural stone. And some varieties of jewelry and semiprecious stones (such as charoite, chrome-diopside, and garnets of the pyrope-almandine group, most of topaz and tourmaline, and a number of others) are generally not profitable in production.
So the average price of the most popular jewel inserts from synthetic analogs of natural stones usually does not exceed 10% of the cost of natural stones of the corresponding mineral type with the same quality properties. However, it should be noted that synthetic stones are not complete copies of natural stones and have traces of the corresponding production process.
There are two main types of emerald deposits - greisen and hydrothermal, which differ in the type of enclosing rocks and accordingly the conditions of crystallization of beryl and its varieties (including emeralds).
The main world centers for the emeralds mining today are Colombia (about 60% of the market), Zambia and Brazil. Smaller deposits of emerald raw materials are also found in Zimbabwe, Madagascar, Mozambique, South Africa, China, India, Afghanistan, Kazakhstan and Central Asia.
Emeralds of different genesis are characterized by certain features that allow the expert-gemologist to qualify them by the type of deposit.
One of such signs is the color of the emerald, which can indicate the origin of the stone indirectly. So Colombian emeralds are characterized by a bright green color with blue hues, emeralds of Zambia often show blue tones, and Uralic samples are distinguished by the presence of yellow shades in the color range of emeralds.
However, color is not an absolute criterion for definition the genesis of emeralds. A more accurate classification of this stones type by their origin occurs by using a complex of spectral diagnostic methods.
Another visual distinctive property is the specific form of multiphase inclusions and its composition. For example, emeralds from Afghanistan and Colombia have a similar distinctive "saw-like" form of polyphase inclusions, but differ in the composition of solid phases. There are microinclusions of quartz and siderite in emeralds from Afghanistan, and calcite and dolomite in Colombian emeralds.
There are two concepts "diamond imitation" and "synthetic diamond" which are often confused.
Imitation is a material (in our case a mineral) that has an external resemblance to the object of imitation but differs from it in composition and physical properties. Unlike simulation the synthetic analog of the material is similar to the natural analog of the chemical composition (without taking into account impurities obtained during the synthesis) and properties.
Moissanite and phianite are the most common in the market of precious stones of imitation of a diamond, having a synthetic origin.
Moissanite is a mineral of SiC (silicon carbide) hexagonal system, rare on Earth and widely distributed in space. At the turn of the 1990's and 2000's, artificially grown moissanite found application in the jewelry industry as an independent jewelry material and as an imitation diamond. The external similarity of moissanite and diamond is due to similar values of these minerals. You can distinguish imitation by the noticeable birefringence properties of all anisotropic stones, and by specific tubular microinclusions.
Phianite is an artificial material that does not have complete analogs in nature. The composition and crystallographic structure is zirconium dioxide ZrO2 with an artificially stabilized cubic crystal system. The main diagnostic feature of phianite is its very low thermal conductivity in comparison with a diamond. The proximity of the refractive index of the diamond and its imitations ensures their external similarity however differences in hardness and density make it possible to easily distinguish "not a diamond".
Synthetic diamond is a mineral with a chemical composition corresponding to the native carbon of the cubic system and outwardly completely analogous to the natural, differing only in origin. In this connection, it is possible to distinguish a synthetic diamond from imitation in exactly the same way as a natural one.
There is a technique for weight calculation of fixed inserts by linear dimensions without attaching them.
In this case, the insert standard weight is firstly determined basing on its linear dimensions and using a coefficient depending on the shape of the insert.
To obtain a more accurate result, there are corrections for the thickness of the girdle, for breaking the symmetry of the cut, for convexity of the crown and pavilion, which are introduced in the calculation.
The satisfactory accuracy of weight measurement, taking into account all the corrections, is determined within ± 5%. However, it is necessary to take in mind the possible error in measuring the dimensions depending on the degree of availability of the insert in the product for use by the measuring instrument, and also the openness of the insert to the visual survey which makes it possible to evaluate the factors affecting the shape and symmetry of the weight. Thus, the satisfactory accuracy of the weight measurements for an inaccessible insert can be at ± 15%.
Detectors of diamonds based on thermal conductivity of minerals practically do not distinguish a diamond from moissanite because of their practical coincidence of the values of thermal conductivity of these minerals.
When using detectors based on combined heat and electric conductivity indicators it is possible to reduce the error percentage but not to bring them to zero (some moissanites are defined as diamonds and vice versa), which is related to the electrochemical properties of some types of diamonds and moissanites with alloying additives.
Detectors based on the measurement of refractive index (refractometers and reflectometers) may "not notice" stones with a "thick" narrated diamond-like or diamond layer.
Absolute results (including "layer-by-layer" determination in the sample) are provided by Raman spectrometry, but the disadvantage of this method include the high cost of the instrumentation and software-analytical base.
To classify appraisal value of a diamond you need to have information about the origin of the diamond (natural or synthetic), enhanced or untreated diamond, its main estimated (4Cs - carat, color, clarity, cut) and additional (luminescence) characteristics.
Having all the necessary data one should refer to the evaluation sheet of one of the main indicators of the market for cut diamonds (Rapaport, IDEX, The Guide, etc.) and to define the appraisal value of the diamond on the main evaluation sheet then take into account the discount for luminescence, type of gemological conclusion or stone certificate, and trade discounts for your market segment (based on the type of transaction of purchase and sale).
The resulting figure will define the value of your diamond with an accuracy of ± 20% for the region covered by the market indicator.
You can also study the offers and discounts of sales agents (dealers and retailers) in the diamond market in your region yourself but this method although it gives higher accuracy in value estimation of your stone requires much more effort and time. But to proper estimation of the market value without errors you need to contact the relevant qualified specialists.
The term "oiling" regarding to the emerald is a common, acceptable and reversible kind of enhancing of the gem in order to improve the visual performances of the clarity. Oiling is a kind of enhancing that is diagnosed visually. Oiling is the most common type of enhancing the emerald.
This type of enhancing has a number of disadvantages along with advantages:
- enhanced stones require a very neat approach to cleaning since oil is easily removed by many modern detergents;
- enhanced stones are undesirable to heat so oil can escape from cracks on the surface of the stone as a result of thermal expansion;
- oil treated stones must be cleaned from time to time and re-processed as the oil eventually polymerizes and becomes cloudy.
Sometimes emeralds are enhanced in two parameters at once (both in clarity and in color) using colored oil for impregnation. This kind of enhancement is not acceptable as it is often applied to stones that are not emeralds by definition.
HPHT technique is a complex process of combining high temperatures (at least 900°C, but usually above 1500°C) and high pressures (thousands of atmospheres) on a diamond (or diamond in raw materials). As a result of such processing, a kind of "release" of the diamond occurs - internal stresses disappear, twins dissolve, structural defects change. The result of such transformations is a change in the physical and chemical properties of diamond in particular color which is the main reason for such enhancement. HPHT enhancement is not reversible.
The HPHT treated stones are estimated much cheaper than similar ones (having the same quality properties) unlike untreated ones.
Diamonds with low clarity performances are treated by filling the cavity crack with high refractive glasses in order to visually improve the clarity. This type of treatment is irreversible and visually diagnosed.
The advantages of stones treated this way are relatively low price at considerable sizes.
The disadvantage is the fact that such stones cannot be cleaned in ultrasonic washing as well as washing in corrosive environments (acids, strong alkalis). Also stones filled with glass should not be exposed to long-term exposure to ultraviolet radiation of high intensity since there is a possibility of haziness of the glass in the cracks.
Jewelry with the platemark of the Russian Federation can be sold in several ways:
- To pawn the jewelry without redemption. The disadvantage of this method is the least profitability, since the pawnshop gets the extra charges in the process of preparing products for public sales, and is also required to store your products for some time (the so-called grace period), which increases the extra charges.
- Purchase. The fastest way to sell jewelry or scrap, but the price for this method of sale is not much higher than the funds received in the pawnshop (the cost of scrap minus the extras of a particular organization).
- Sale through the commission agent (antique, commission jewelry stores). This is the longest way to sell. The advantage is that the seller can set a price corresponding to the market price of the product.
- The sale of jewelry owned by an individual (personal property) to another individual is possible in case if there is no commercial profit from the seller only.
Sale of jewelry by individuals that are not registered as subjects engaged in jewelry trade in the Russian Federation for commercial profit is illegal.
Diamonds may be subject to civil goods turnover (purchase and sale) either as part of a jewelry or in the form of a certified stone in the Russian Federation. The sale of jewelry can be made through the sparse organizations, pawnshops, commission stores and in the form of sale by an individual to an individual (provided that the jewelry is in the seller's personal property and the seller does not have commercial profit). Sale of certified diamonds is possible through commission shops and from an individual to an individual (provided that a certified diamond is in the seller's personal property and the seller does not have commercial profit).
Sale of jewelry and certified diamonds by individuals that are not registered as subjects engaged in jewelry trade in the Russian Federation for commercial profit is illegal.
Plotting is the identity diagram of a diamond (sometimes a colored stone), which includes a schematic image:
- stone cut in the projection on the girdle plane, separately the crown scheme and separately pavilion scheme conjugated along the turn axis;
- location, shape and conditional size of internal and external significant factors of clarity (defects).
Plotting is used to facilitate the identification of a particular stone, as well as to clearly indicate the factors of clarity in the secondary viewing of the stone.
Heat treated sapphire is a natural sapphire that has undergone some type of heating process in order to alter or improve its appearance.
Natural sapphires are usually heat treated to improve color and clarity. As a result of the dissolution of mineral inclusions and the chemical reactions occurring in the mineral, the blue color of the stone intensifies or undesirable shades disappear, and also it improves the clarity of the stone. This type of treatment is worldwide accepted and is acceptable for stones that do not belong to the highest quality categories.
Nowadays cat’s eye gemstone is just the common referring term for the phenomenon of chatoyancy where moving the gem under a source of light gives the appearance similar to opening and closing of a cat eye. The optical phenomenon of the cat’s eye is a kind of iridescence, displayed on the surface of the stone in the form of a narrow floating light strip, which is formed as a result of the reflection of incident light from regularly located internal inclusions (parallel columns, tubes, plates). Initially the term "cat's eye" was applied to yellow-green chrysoberyl with the corresponding optical effect but later this name with the refinement of the mineral form where the effect was shown was applied to all other stones - tourmaline cat's eye, quartz cat's eye, heliodorous cat's eye and others.
Diffusion sapphire is a natural sapphire that has undergone some type of diffusion process in order to alter or improve its appearance.
Diffusion treatment of sapphires is used for both natural and synthetic stones in order to improve the quality of color. This kind of treatment is irreversible. The essence of the method consists in the artificial chemical diffusion of sapphire as a result of heating in a medium with a composition that causes a change in color at the structural level. In most cases this coloration is of a near-surface character and can be eliminated by means of re-cutting (and even re-polishing). But some methods of diffusion can cause a change in the entire stone.
Rubies and sapphires often have the effect of asterism sometimes in everyday speech called "star". Asterism is a special case of iridescence in the shape of a light star formed due to reflection from regularly located internal inclusions and inhomogeneities. Most often asterism is associated with the inclusion of rutile in rubies and bohmite in sapphires, but the reasons that cause this kind of iridescence may be in other heterogeneities of the mineral composition and stone structural configuration. Nowadays artificial creation of the effect of asterism in corundums as a result of special diffusion is widespread.
The name "Paraiba" is applied to the Cu- and Mn-containing tourmaline (namely to the elbaite), with a color range from green to blue with a purple hue. It was discovered in Paraiba, Brazil pegmatites. Later similar tourmalines were found in other states, as well as in Africa - Nigeria, and later in Mozambique. Since 2007 (in accordance with the decision of the LMHC of April 20, 2007) the following description of these tourmalines has been adopted:
Supergroup - Tourmaline; Mineral species - Elbait; Variety is Paraiba.
Sometimes in gemmological conclusions and in trade the formulation is used: Tourmaline, "paraiba" type.
The largest cut diamond today is a yellow-brown stone called "Golden Jubilee". The carat weight of the diamond that has the shape of an oval cushion, is 545.67 ct. Diamond was cut from a 755-carat rough stone that was discovered in the Premier mine in South Africa in 1985. Diamond cut was made under the direction of Gabriel Tolkowski from 1988 to 1990. The name was given to the diamond in 1995, when it was presented to the king of Thailand, Rama IX, in honor of the 50th anniversary of the coronation. Currently, this largest cut diamond is exhibited in the Golden Temple in the Royal Museum (Bangkok).
The group of companies (Rapaport Group) was founded in 1976 with the aim of providing information, consulting and infrastructure services in the development of the diamond, cut diamond and jewelry market.
The publishing department that publishes the periodical Rapaport (Rapaport Magazine) was established in 1978. This publication covers the main issues related to the diamond mining and diamond treatment business. The most famous section of the magazine relates to the review of auctions and "Rapaport Price Lists" - an information sheet reflects the diamond price level in the market of New York (USA).
Voluntary certification is a service performed basing on a civil contract between a customer and an executor (contractor), which grant the compliance with the requirements of technical regulations, standards, etc. The document of the certification result basing on the results of the expertise is a certificate issued on the basis of the test report (expert report).
Voluntary certification in the precious stones market is needed to ensure consumer rights. Certification allows you to identify (or maximally hamper) both goods seller unfair competition and fraudulent misrepresentation or direct forgery.