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Showing posts from November, 2023

Gemstone Windows and Dark Patches: What to Look for in a Cut Gem

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AI-generated educational illustration. Conceptual only; not a photograph of an actual specimen or location. A coloured gem may have a pale, see-through centre or areas that look almost black. Both affect its appearance, but they do not have the same cause. What is a window? A window is an area where light passes through the gem instead of being returned towards the viewer. You may see the background through it, especially near the centre. Cutting angles and the material's refractive index—how it bends light—help determine whether this happens. There is no single ideal depth for every gemstone. Why dark patches need a closer look Darkness can have several causes. The material may absorb a lot of light. Some facets may reflect dark surroundings or the observer. Extinction is another cause, involving light that is not returned to the viewer after internal reflection. For that reason, calling every black patch “extinction” can be misleading. A simple viewing routine Look at the gem fac...
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Gemological Refractometer

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  Refractometer Construction of Refractometer A refractometer consists of a light source, a contact liquid chamber, and an optical system for measuring the refractive index of a substance. Sources of Illumination (Sodium Light) Sodium light is commonly used as a source of illumination in refractometers due to its monochromatic nature. Contact Liquid The contact liquid is used to ensure proper contact between the substance being measured and the refractometer prism. It helps minimize air gaps and improves the accuracy of the measurement. Using the Refractometer To use the refractometer, follow these steps: Place a few drops of the contact liquid on the prism. Open the cover plate and ensure the prism is clean and dry. Close the cover plate and wait for the temperature of the refractometer to stabilize. Open the cover plate again and place a drop of the substance being measured on the prism. Close the cover plate and look through the eyepiece. Taking Reading To take a reading, observ...
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Cause of Color in Gemstones

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  Cause of Color in Gemstones Selective Absorption Selective absorption is one of the main causes of color in gemstones. Certain gemstones have atoms or ions in their crystal structure that selectively absorb certain wavelengths of light. The absorbed wavelengths correspond to the colors that are seen by our eyes, giving the gemstones their characteristic color. Residual Color Residual color refers to the color that remains in a gemstone even after all impurities have been removed. This residual color is caused by the presence of trace elements or defects in the crystal lattice of the gemstone. The Transition Elements The transition elements, such as chromium, iron, and titanium, can cause color in gemstones. These elements can replace certain atoms in the crystal structure of the gemstone and give rise to different colors. Crystal Field Transitions Crystal field transitions occur when electrons in the crystal lattice of a gemstone absorb or emit light energy. These transitions are...
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Heavy Liquid Method - Specific Gravity

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  Heavy Liquid Method - Specific Gravity Specific Gravity Specific gravity is a measurement used in the heavy liquid method to determine the density of minerals. It is the ratio of the density of a substance to the density of a reference substance (usually water). Specific gravity is a dimensionless quantity. In the heavy liquid method, specific gravity is used to determine the appropriate heavy liquid to use for mineral separation. Each heavy liquid has a specific gravity that allows it to separate minerals based on their density. Types of Liquids and Their Uses Tetrabromoethane (TBE):  Used for separating minerals with a density greater than 2.85 g/cm³. Sodium polytungstate (SPT):  Used for separating minerals with a density between 2.85 g/cm³ and 2.95 g/cm³. Diiodomethane (DIM):  Used for separating minerals with a density less than 2.95 g/cm³. Precautions Handle the heavy liquids in a well-ventilated area or under a fume hood to avoid inhaling any fumes. Wear app...
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Gemological Microscope and its uses

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  Gemological Microscope and Use of Illuminations Techniques The gemological microscope is an essential tool in gemology as it allows gemologists to observe gemstones at high magnification, revealing their internal features and characteristics. Here are some key points about the gemological microscope and its various illumination techniques: Features of the Gem Microscope High magnification capabilities Adjustable focus and zoom Built-in light source Ability to attach a camera for documentation purposes Types of Illumination Reflected/Incident Illumination:  This technique uses a light source positioned above the gemstone to illuminate it from different angles. It helps to reveal surface features, such as scratches and polishing marks. Dark Field Illumination:  In this technique, the light source is positioned at an angle, causing the gemstone's facets to reflect light only when they have inclusions or defects. It enhances the visibility of internal features. Direct Light...
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Rare Earth Elements (REE) and its unique properties

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  Rare Earth Elements Rare earth elements (REEs) are a group of chemical elements that are essential in various industries due to their unique properties. Here are some of the rare earth elements and their uses: Element Uses Scandium Alloying agent in aerospace components, improves the performance of solid oxide fuel cells, enhances the properties of aluminum alloys, used in high-intensity discharge lamps, used in sports equipment like baseball bats and bicycle frames for its lightweight and high-strength properties Yttrium Used in superconductors, phosphors for color televisions, lasers, and solid-state lasers, catalysts in petrochemical refining, and as a component in ceramics and glass Lanthanum Used in hybrid car batteries, camera lenses, high-refractive-index glass, catalysts in the petroleum industry, and as a component in ceramics and glass Cerium Used in catalytic converters, self-cleaning ovens, polishing agents, and as a component in glass, enamels, and ceramics Praseodym...
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Location: Germany
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Jermejevite (Rare Mineral)

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  Jermejevite (Rare  Aluminium Borate Mineral)   1. Introduction to Jeremejevite Jeremejevite is a fascinating mineral that has captured the attention of gemstone enthusiasts and mineral collectors alike. Known for its striking blue color and hexagonal crystal structure, this gemstone has a unique beauty that sets it apart from other minerals. In this article, we will delve into the crystal structure and physical properties of jeremejevite, its formation and occurrence in nature, as well as its intriguing historical background and discovery. 2. Crystal Structure and Physical Properties 2.1 Hexagonal Crystal System Jeremejevite belongs to the hexagonal crystal system, which gives its crystals a distinct six-sided prismatic shape. This hexagonal symmetry is responsible for the gemstone's mesmerizing appearance and exceptional optical properties. 2.2 Prismatic Crystal Habits Crystals of jeremejevite are typically seen in a hexagonal prismatic habit, with well-formed faces an...
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