The secret of identifying the stratification of precious stones

In this article, we have used the help of experts from Hanar Holding to provide specialized information in the field of expertise and identification of precious, semi-precious and diamond stones, and we hope that this information can be used by activists in this field.

The secret of identifying the stratification of precious stones

Gemstone identification techniques

Gemstone identification relies on a combination of techniques to determine the physical, optical, and chemical properties of a gemstone. These techniques range from simple visual observations to advanced analytical methods using specialized gemological tools.

Physical properties:

A gemstone’s physical properties, such as its color, luster, clarity, and crystal system, provide important clues to identification. Gemstones can be categorized based on their color, which can range from colorless to vibrant colors. Luster refers to the way a gemstone reflects light and can be described as adamantine (diamond-like), vitreous (glassy), or pearlescent. Clarity refers to how well light passes through a gemstone and can be classified as clear, translucent, or opaque. The crystal system, which describes the internal atomic arrangement, can also help with identification.

Optical properties:

Precious stones exhibit unique optical properties that can be seen using specialized instruments. Refractive index (RI) measures the amount of bending of light as it enters and exits a gemstone and is an important identifier for many gemstones. Birefringence or birefringence occurs in anisotropic gemstones and can create distinctive optical effects. Pleochroism, the ability of a gemstone to show different colors when viewed from different angles, is another important optical property.

Chemical analysis:

Advanced analytical techniques, such as X-ray fluorescence (XRF), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR), can reveal the chemical composition of a gemstone. These methods can detect the presence of specific elements or molecular structures and provide valuable information to identify and differentiate between natural and synthetic gemstones.

Gemological tools:

A variety of specialized tools are used to identify precious stones. A refractometer measures the refractive index of a gemstone, while a polariscope helps identify optical properties such as pleochroism and birefringence. Microscopes, both standard and submersible types, allow detailed examination of internal features and components. Spectroscopy analyzes the absorption and emission spectra of gemstones and provides chemical information. Other instruments, such as specific gravity scales, hardness testers, and ultraviolet lamps, can show more physical and optical properties.

By combining these techniques and using the appropriate gemological tools, gemologists can accurately identify and distinguish different types of gemstones and ensure proper grading, valuation, and authentication.

Official Bachelor of Antiques

Visual examination of art and precious stones

Visual inspection is the first and most basic step in identifying and authenticating art and precious stones. It involves careful observation and analysis of various physical features using the naked eye or low-magnification instruments. Here are some key aspects to consider:

color
Color is an important aspect in identifying art and gemstones. In art, an artist’s choice of colors, their combination, and how they are applied can provide valuable insight into a work’s originality, period, and artistic style. For gemstones, color is often the most distinguishing characteristic and can indicate the type of gemstone, its origin, and any potential treatments or enhancements.

Texture and brush stroke
Texture and brushwork in a painting can reveal important information about the artist’s technique, the materials used, and the age of the work. Careful examination of brushwork, impasto (thick paint application), and surface texture can help authenticate a painting and distinguish it from a fake or reproduction.

Includes defects
Both art and gemstones may contain inclusions or imperfections that can be valuable clues to identification. In paintings, components such as craquelure (fine cracks in the paint), pentimenti (visible changes made by the artist), and underpainting can provide insight into the work’s creation process and authenticity. For gemstones, inclusions are unique internal features that can help identify the gemstone’s type, origin, and potential treatments.

Cut and transparency
While not directly applicable to artistic identification, the cut and clarity of a gemstone are fundamental factors in determining its value and quality. Cut refers to the precise arrangement of the facets of a gemstone, which can affect its brilliance and fire. Clarity refers to the presence or absence of spots and blemishes that can affect the clarity and overall appearance of the gemstone.

By carefully observing these visual features, experts can gather valuable information for authenticating and evaluating art and gemstones. However, visual examination must be combined with other techniques, such as provenance research and material analysis, for a comprehensive identification process.

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Properties of precious stones and identification

The identification of precious stones relies on a thorough investigation of various physical and optical properties. These features act as unique fingerprints and enable gemologists to accurately identify and distinguish different types of gemstones. Here are some key properties used to identify gemstones:

Refractive index (RI):

The index of refraction measures the speed of light passing through a gemstone compared to its speed in a vacuum. This is a critical feature for identifying gemstones, as each gemstone has a unique RI or range of RIs. Gemologists use a refractometer to measure RI, which can help distinguish between diamonds, cubic zirconia, and other gemstones.

Specific gravity (SG):

Specific gravity, also known as relative density, is the ratio of the weight of a gemstone to the weight of an equal volume of water. This is a valuable identification tool because each gemstone has a characteristic SG range. Gemologists use specialized tools such as hydrostatic balances or specific gravity fluids to determine a gemstone’s SG.

Difficulty:

Hardness refers to a gemstone’s resistance to scratching or wear. The Mohs hardness scale, which ranges from 1 (talc) to 10 (diamond), is used to measure the hardness of a gemstone relative to other minerals. Gemstones with a higher hardness value are more resistant to scratching and wear, making hardness a key factor in determining a gem’s suitability for jewelry.

Dispersion:

Scattering, also known as fire, is the separation of white light into its spectral colors as it passes through a gemstone. This is a measure of a gemstone’s ability to emit different wavelengths of light. Gemstones with higher dispersion, such as diamonds, show more intense flashes of rainbow colors, adding to their brilliance and beauty.

Fluorescence:

Some gemstones exhibit fluorescence, which emits visible light when exposed to ultraviolet (UV) radiation. Fluorescence can be a useful identification tool because different gemstone species may exhibit unique fluorescence colors or intensities under UV light. Gemologists use specialized UV lamps to observe and document the fluorescence behavior of a gemstone.

By scrutinizing these characteristics, gemologists can accurately identify and differentiate between different types of gemstones, ensuring that consumers and collectors are receiving authentic and correctly identified gemstones.

Accurate detection of stones

Gemological tools

Gemological tools play an important role in the accurate identification and evaluation of precious stones. These specialized tools provide valuable insights into the physical and optical properties of gemstones and enable gemologists and jewelry specialists to distinguish between natural and synthetic stones, as well as determine their quality and value. The most common gemological tools used are: microscope, refractometer, spectrometer, polariscope and diamond tester.

Microscope:

A microscope is an essential tool for examining the internal characteristics and components of precious stones. They allow gemologists to see fine details that are not visible to the naked eye, such as growth patterns, fractures, and impurities. Microscopes can reveal the presence of natural or artificial components that can help identify the origin and authenticity of a gemstone.

Refractometer:

Refractometers measure a gemstone’s refractive index, which is a fundamental property that determines how light travels through the material. By measuring the refractive index, gemologists can identify the type of gemstone and differentiate between natural and synthetic types. Refractometers are particularly useful for distinguishing between diamonds and their imitators, as well as for identifying gemstones with similar appearance but different refractive indices.

Spectrum:

Spectrometers analyze the absorption and emission of light in different wavelengths by precious stones and create a unique spectral pattern. This pattern is known as the gemstone’s absorption spectrum and can be used to identify the gemstone’s chemical composition and detect any treatments or enhancements. Spectroscopes are especially useful for identifying rare and exotic gemstones, as well as for identifying artificial stones.

polariscope:

Polariscopes are instruments that use polarized light to examine the optical properties of gemstones. They can reveal the presence of strain patterns, twin plates, and other internal features that characterize certain gemstone types. Polariscopes are especially useful for identifying gems with crystalline structures such as diamonds, rubies, and sapphires.

Diamond tester:

Diamond testers are specialized devices designed to distinguish diamonds from their imitators such as cubic zirconia and moissanite. These testers work by measuring thermal conductivity or electrical conductivity

Precious stones, which are one of the unique properties of diamonds, diamond testers are an essential tool for jewelers and gemologists to quickly and accurately identify diamonds.

Using this gemological tool, gemologists and jewelry specialists can accurately identify and evaluate gemstones, ensuring that customers receive authentic, high-quality products. Additionally, these tools help identify any treatments or enhancements applied to gemstones and promote transparency and ethical practices in the gemstone industry.

Millstone detection

About certification and grading of art and precious stones

Professional certification and grading are vital aspects of the art and gemstone industry, providing authentication, quality assurance and valuation. These processes include careful review by experts and the use of standardized grading systems.

For works of art, certification usually involves authentication by recognized authorities or institutions. Art experts carefully analyze provenance, materials, techniques, and stylistic elements to determine a work’s authenticity and attribution. Reputable organizations such as auction houses, museums, and art authentication boards issue certificates of authenticity or opinions, which serve as valuable documents for collectors, dealers, and insurers.

Certification of gemstones is primarily done by independent gemological laboratories. These laboratories employ highly trained gemologists who use advanced techniques and tools to evaluate a gemstone’s characteristics, including its color, clarity, cut and carat weight. The most well-known gemstone grading systems are those developed by organizations such as the Gemological Institute of America (GIA) and the American Gemological Society (AGS). These systems provide a consistent and objective means of evaluating gemstone quality, enabling buyers and sellers to make informed decisions.

The grading reports or certificates issued by these laboratories provide detailed information about the gemstone’s characteristics, quality, and rarity. These reports also include a quality grade based on the specific grading system used, making it easier to compare and accurately value gemstones.

In addition to authentication and grading, professional appraisals are critical to determining the monetary value of art and gemstones. Qualified appraisers consider various factors such as rarity, condition, provenance, market demand and historical significance to arrive at a fair market value. Appraisal reports are often required for insurance purposes, estate planning, and legal disputes.

It is important to note that the certification, grading and assessment processes should be carried out by professionals or reputable and accredited organizations to ensure accuracy, transparency and adherence to industry standards. These processes not only protect the interests of buyers and sellers, but also contribute to the overall integrity and credibility of the art and gemstone markets.

Diamond detection

Legal and ethical considerations

Identifying art and gemstones has significant legal and ethical implications. One of the primary concerns is the prevalence of counterfeiting and fraud in these industries. Fake artwork and synthetic gemstones can mislead buyers, undermine market integrity, and potentially involve criminal activity. Provenance, or the documented history of ownership, is critical to verifying the provenance and authenticity of art and gemstones.

Import and export regulations also play a vital role in the legal trade of art and precious stones. Many countries have implemented strict laws to prevent the illegal trafficking of cultural heritage objects and to combat the financing of organized crime or terrorist activities through the sale of looted antiquities or conflict gems. Compliance with these regulations is essential for collectors, sellers and institutions alike.

In addition, the protection of cultural heritage is an important ethical consideration. Some art objects or precious stones may have great historical, cultural or religious significance for certain communities or nations. Responsible measures must be followed to ensure that these items are preserved and treated respectfully and to prevent their exploitation or destruction.

Transparency and ethical sourcing are very important in the art and gemstone business. Sellers, auction houses and other industry professionals are responsible for conducting due diligence, disclosing relevant information to buyers, and following best practices to maintain integrity and trust in these specialty markets.

Diagnosing diamond stones

Case studies and examples

Vinland map controversy
In the 1950s, a parchment map known as the Vineland Map appeared, purporting to show Norse exploration of North America centuries before Columbus. The authenticity of the map was initially accepted, but subsequent analysis revealed evidence of forgery, including the use of ink, highlighting the importance of careful scientific analysis in art authentication.

Dresdner Bank Black Diamond
In the 1980s, the Dresdner Bank in Germany acquired a large black diamond for its collection. Initially thought to be a rare carbonado diamond, further examination by gemologists revealed that it was actually an exceptionally large piece of polycrystalline lonsdaleite, an even rarer form of diamond. This case demonstrates the challenges of identifying unique and unusual gemstones.

Clay Army cheats
After the discovery of the famous Clay Army in China, a thriving black market emerged for fake clay warriors and other artifacts. Skilled forgers used ancient techniques and materials to create convincing fakes, making authentication a complex task for experts. This case emphasizes the need for comprehensive authentication methods, including material analysis and provenance research.

Revelations of Rembrandt
Over the years, several paintings have been attributed to the Dutch master Rembrandt van Rijn, but later reattributed or declared to be fakes. Advanced techniques such as X-ray analysis and pigment analysis have helped to authenticate genuine Rembrandt works and expose fakes. This ongoing process demonstrates the evolving nature of art authentication and the importance of staying current with the latest methods.

Mozu Emerald Mine
The Muzo emerald mines in Colombia have produced some of the world’s finest emeralds, but they also present numerous challenges in identifying gemstones. Treatments such as oiling and dyeing, as well as the presence of synthetic and imitation emeralds, have made it necessary for gemologists to use advanced techniques such as spectroscopy and microscopic analysis to authenticate these precious gems.

Organizations and professional associations where you can get specialized information

– International Association of Assessors (ISA)
– American Association of Appraisers (AAA)
– American Association of Appraisers (ASA)
– Gemological Institute of America (GIA)
– American Gemological Society (AGS)
– International Institute of Gemology (IGI)

This article was created with more than 100 hours of work by the expert team of Art Holding, and its copying is definitely not allowed except with the name of the reference and the original source; Iranian Art Holding

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