The Meditations Series Meditations Meditations. It was the first topic he mentioned in his first sermon, and the last topic he mentioned in his last. These edited transcripts correspond to the 13 Noble Eightfold Path mp3s available on the Talk Collections page.
Let's take an example: But under what conditions would I have an example of a synthetic, a simulant and a fake ruby? Gemstones First things first: According to FTC regulations, which guide the gem and jewelry industry's trade and advertising, only natural mineral and organic materials can be legally and ethically sold and advertised as "gemstones".
Other terminology, such as "synthetic" or the equivalent terms "cultured", "created" or "laboratory grown" must be used for materials which did not originate in Nature. Synthetics A synthetic has been manufactured in a laboratory or factory.
Synthetics may or may not have natural analogs. Synthetic ruby, for example, is a man-made version of natural ruby and is virtually identical to it in both chemical composition and crystal structure.
As a result both types show the same physical and optical properties like density and refractive index. Yttrium aluminum garnets, YAG, in colorless Essays and compositions green. The first synthetics, produced in a size and at a cost to make them marketable, were synthetic rubies made by August Verneuil around Many people don't realize that synthetics go that far back, and have been bitterly disappointed to find that the wonderful Edwardian or Art Nouveau ring they inherited from Great Aunt Minnie was set with a synthetic!
In fact, synthetics were, for a while, with some designers, kind of the "cool new thing" and were not relegated to second tier or mass produced jewelry as they tend to be today. Image courtesy of Acanthus Antiques, Art Deco circa 's Platinum, diamond, natural pearl necklace, set with synthetic sapphires on the clasp] The process Verneuil developed, called "flame fusion" is still the main one being used to produce synthetic corundum and synthetic spinel.
A powdered source material, like aluminum oxide for corundum with, a metallic oxide such as chromium oxide to provide the red color, is melted. As it drops through an oxy-hydrogen torch flame the molten material crystalizes as it hits a ceramic platform at the, cooler, base of the furnace.
As the crystal grows the platform is turned and lowered, creating a carrot-shaped "boule".
Because synthetics have the same optical, chemical and physical properties as the natural materials they mimic, standard gemological tests are not very useful in identifying them.
In these cases the microscope becomes a gemologist's most valuable tool in separating the synthetics from gems of natural origin.
There are microscopic inclusions which occur only in natural gems, and those which occur only in synthetics.
Unfortunately, there are also many inclusions which can occur in either type, and flawless stones with no inclusions to see. The flame fusion materials are usually the easiest type of synthetics to discriminate from their natural counterparts.
The most definitive sign is known as "curved striae" which under magnification, in diffused light, look a bit like the grooves on an old vinyl recording. Curved striae in a flame fusion corundum Triangular platinum crystals from the crucible such as seen in a "flux melt" synthetic Alexandrite are another absolute indicator of synthetic status.
Some of these, like the hydrothermal process, which is responsible for so much of the synthetic emerald in commerce, mimic the conditions of Nature, others likeVerneuil's are entirely human inventions.
Simulants A simulant is any material, natural or synthetic, that looks like, and is used in place of, another material natural or syntheticbut is not represented to be the natural gem.
The term, "imitation" is equivalent to simulant. For example a natural simulant of ruby is the gemstone, red spinel which can have a color and luster very like that of a ruby. On the other hand, red, man-made glass has long been used as an inexpenisve ruby simulant.
Simulants have been around since antiquity. As early as BC, Eqyptians produced a non-clay, ceramic compound, colored by copper, called faience with an appearance very similar to turquoise. Today this dispersive type of leaded glass, is generally marketed as "crystal" a misnomer, of course, since all glasses are amorphous, not crystalline.
Simulants are less common than they once were as the availability of relatively inexpensive synthetics for many materials have made them less desirable.English for Specific Purposes World, ISSN , rutadeltambor.com, Issue 40, vol. 14, Error Analysis of Written English Essays: The case of Students.
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