Gemological (mineralogical) examination

The solution of identification problems within the framework of a gemological examination makes it possible to establish:

• common source of origin of stones;
• whether they previously constituted a single whole (including one set), parts of the jewelry (to be decided within the framework of a comprehensive examination).

The main types of work for gemological examination :

• instrumental diagnostics of stones, including determination of their origin (natural or artificial) and identification of refinement;
• recognition of imitations and fakes;
• determination of the quality characteristics of stones;
• forecasting the cost of stones in jewelry and other products, raw materials, collection and museum exhibits, etc .;
• services for the examination of lots of precious stones for technical purposes.

Expert examination techniques for minerals include:

• methods for determining mechanical properties: hardness, fragility, cleavage;
• methods for determining optical properties: transparency, color, pleochroism, refraction, luminescence;
• methods for determining the density of minerals;
• microscopic methods: optical, X-ray and electron microscopy, which allow studying the signs of the external and internal structure of minerals (inclusions, cracks, the nature of the distribution of color, etc.).

X-ray methods for the analysis of minerals:

• X-ray diffraction (including X-ray phase) analysis is a classic method for diagnosing minerals, it makes it possible to determine the mineral type, structural varieties, to give a qualitative and quantitative assessment of the composition, to obtain information on the fineness of a substance, structure defectiveness, etc.;
• X-ray spectral analysis - to establish the qualitative and quantitative elemental composition of minerals and their inclusions;
• X-ray luminescence.

For example, determining the type of precious stones involves measuring and evaluating the following indicators: color, refractive index, hardness, luminescence, pleochroism, etc.

Gemological (mineralogical) examination is carried out using instrumental methods and with the help of modern equipment:

• D-Scope microscopes;
• refractometers;
• ICh-Fourier - spectrometer;
• X-ray energy spectrometer;
• special fluorescent lamps;
• laser diamond scanner OGI, etc.

The characteristics of gemstones are determined in accordance with the Technical Conditions and Regulations of the State Heritage Site, in accordance with methods traditional for the CIS countries and international rules.

Given the range of methods of gemological examination, it is performed by experienced specialists who have higher education and special qualifications obtained in leading gemological centers.

Based on the results of the examination, an expert opinion is issued in the form approved by the Ministry of Finance of Ukraine.

A special issue of gemological expertise is the issue of marking precious stones. The marking of precious stones is established by the current legislation, regulatory and technical documentation.

The marking of a single gem of natural origin or a batch of loose gemstones should contain information on the quality characteristics that are applied to the jewelry label, paper bag or to a special form. For example, for a diamond, the following information is noted:

1. proper name of the stone: "diamond" (only for natural diamonds), "artificial synthetic diamond" (for artificial diamonds);
2. weight (for one diamond) or total weight
3. dimension or weight subgroup and number of diamonds (in pieces) - for a batch of diamonds;
4. name of the type of cut;
5. a group of geometric parameters, a group of purity and a color group (except artificial).

Also, during gemological examination, issues of falsification and refinement of precious stones are determined.

In modern jewelry, experts pay special attention to precisely determining the fact that precious stones have been refined.

The quality of precious and decorative stones, their consumer characteristics can almost always be significantly improved. But, the world gemological practice testifies that only naturally high-quality stones have a high price. All processing methods do not change the "status" of the natural stone, but require their informative support during the sale. Today, the refining of precious stones is a whole industry with modern methods and materials.

Types of precious stones refining:

• heat treatment - amber, aquamarine, sapphire, ruby, citrine, amethyst, tourmaline;
• radiation treatment - yellow sapphire, topaz, tourmaline, kunzite;
• crack treatment - emerald, ruby;
• oiling - emerald, jadeite, lapis lazuli;
• applying a coloring coating - sapphire;
• discoloration and staining - agate, onyx, coral;
• laser drilling - diamond.

The price of a refined stone is lower than that of a similar one compared to it. According to the rules of the CIBJO (International Confederation for Gemstones, Silver, Diamonds and Pearls), the term "ennobled" means "... an artificially improved appearance or color of a stone by methods other than polishing and cutting." All stones that have been modified (improved) using such methods must be documented as refined. Failure to do so qualifies as counterfeiting and requires liability in accordance with the law. The exceptions are:

1. heat treatment, which results in the formation of a stable color of amber, corundum (rubies, sapphires), beryl, quartz, topaz, tourmaline, zoisitiv;
2. the use of colorless oils, wax or other substances for emeralds, jade, turquoise, etc .;
3. thermal and acid treatment and touch-up of agates;
4. bleaching ivory and coral.

This is primarily due to the stability of the changes obtained and the difficulties arising in identifying the fact of ennobling.