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On the Origin of Digit Patterns in Gem Opal. Some natural opals, mostly from Ethiopia, show a macroscopic finger-like structure called a digit pattern.

On the Origin of Digit Patterns in Gem Opal

This pattern consists of vertical columns that are more or less parallel, separated by a homogeneous matrix of different color, transparency, or play-of-color. This study proposes that digits develop through: (1) the deposition of a homogeneous opal layer and subsequent polygonization in the form of vertical columns; (2) preferential alteration of this layer at the vertical grain and sub-grain boundaries, creating the digit shape; (3) precipitation of a new silica gel in the space between the digits; and (4) the drying and solidification of the opal. Standard Gem Sizes Chart - International Gem Society.

Purpose: Mass produced gem settings come in standard sizes.

Standard Gem Sizes Chart - International Gem Society

If a gem won’’t fit in a standard setting, a setting should be custom made. This involves much more labor and therefore expense. Bear this in mind when purchasing a gem, or selecting a cut for a gem. There are circumstances where the value of a stone makes it worth cutting for maximum yield, then later paying for a custom setting. In other circumstances, the cost of a custom setting isn’’t justified by the value of the gemstone. Sizes: A gem does not need to be the precise size of the setting. Weights: The weights given are for diamonds cut to ideal proportions. How well do you know your gemstones? Learn the expert techniques Get our free, 3-lesson course: The Essential Art of Identifying Gemstones. Thanks for subscribing! Chart - Faceted Gemstone Weight and Size Charts. Comment bien choisir son Rubis. - Monde des Pierres.

Bien choisir son Rubis ?

Comment bien choisir son Rubis. - Monde des Pierres

J’ai longtemps hésité à m’attaquer à ce monument des pierres précieuses qu’est le Rubis. Cette pierre engendre tous les superlatifs chez les experts et professionnels de la Joaillerie. Mon expérience dans les pierres ne remonte qu’à un an et lorsque je lis des articles et avis sur le Rubis, je retrouve généralement toujours les mêmes recommandations. Une couleur qui serait plus belle que les autres, « sang de pigeon », une région qui produirait de plus beaux Rubis que les autres, la Birmanie, des pierres très rares quasiment impossible à trouver dans de grande taille, etc… Lapidaire. Opale commune et Opale precieuse (Opale noble) La biréfringence est égale à la valeur numérique de l'écart maximal entre l'indice de réfraction le plus petit et celui le plus grand dans une matière gemme anisotrope.

Opale commune et Opale precieuse (Opale noble)

Elle se mesure à l'aide d'un réfractomètre de gemmologie. Les valeurs d'écart données dans la base vont légèrement au-delà de l'extrême minimal et de l'extrême maximal afin de tenir compte des éventuelles erreurs de lecture au réfractomètre. La Fluorescence 1.

Introduction La fluorescence est un phénomène qui met en jeu plusieurs facteurs de notre univers : la lumière, notre œil et l’interaction de la lumière avec la matière. Gemmes Pierres, la boutique des pierres précieuses - Gemmes Pierres. La 5XTUV la lampe UVà LED. Lampe de wood ou lumière noire sont les autres appellations des lampes UV. Exemple d'utilisation : .

La 5XTUV la lampe UVà LED. Lampe de wood ou lumière noire sont les autres appellations des lampes UV

Inova lampe de poche LED X5, ultra-violet. Fluorescent Minerals and Rocks: They Glow under UV Light! What is a Fluorescent Mineral?

Fluorescent Minerals and Rocks: They Glow under UV Light!

All minerals have the ability to reflect light. That is what makes them visible to the human eye. Fluorescent Minerals and Rocks: They Glow under UV Light! Andamooka treated matrix Opal. Andamooka matrix opal: Strictly from the sense of its physical formation, all opal is formed in cavities of opportunity.

Andamooka treated matrix Opal

Sometimes the cavities are large as in 'slides' or 'levels' which produce thick solid slabs; sometimes isolated as in a clam shell; and sometimes intruding into fine fissures in hard native stone such as ironstone. But when opal filters into ancient layers of limestone, something truly miraculous occurs. Limestone is formed over millions of years by the death of countless microscopic plants and animals in waters and bays. The Cliffs of Dover are a well known example. The microscopic cavities in limestone prevent the opal from forming what we recognize as solid opal with thick layers of fire.

Limestone appears to us usually as a very white chalk-like stone. But when the matrix is wetted, that unmistakable opal fire is there, and no doubt much time went into thinking about just how this material might be treated. Diamond Prices: Buy/Sell Diamonds - Wholesale Loose diamonds. The Gemstone Project. So, we’ve talked about gemstone cutting flaws, some stellar gemstone lapidaries and other random topics.

The Gemstone Project

Since I’m typically preoccupied with aesthetics I really wanted to hit on more unusual types of cuts that are visually stunning, but are typically less popular, because the stones usually need custom settings built around them, rather than being able to put the stones into cheaper stock settings that hold traditional shaped stones. Now, these lapidaries are more than capable of cutting rounds, ovals, etc, but the stones that they really cut exceptionally tend to be the fancy fantasy shapes. These gemstones are not something you will see anyone else wearing, every single stone is a one of a kind. Hexagon facets, free form beehives, free form, concave cutting, About the Fluorescent Mineral Society. The Fluorescent Mineral Society is an international organization of professional mineralogists, gemologists, amateur collectors, and others who study and collect fluorescent minerals.

About the Fluorescent Mineral Society

The society was founded in 1971 and incorporated in 1993. The FMS is managed and staffed entirely by volunteers from our worldwide membership of around 500. The mission of the Fluorescent Mineral Society is to bring together people who are interested in fluorescent minerals, and to introduce the public to the hobby of fluorescent mineral collecting. This mission is pursued by promoting fellowship and educational activities, and supporting research that increases basic knowledge of fluorescence and fluorescent minerals.

We share knowledge and experience in collecting, identifying, and displaying minerals which exhibit various forms of luminescence including fluorescence, phosphorescence, triboluminescence, and thermoluminescence. Dr. Luminescence, fluorescence and phosphorescence of minerals. Chemical Formula:See OPALE.