In medieval Spain, ghazals were written in Hebrew as well as Arabic. An important writer of Hebrew ghazals, and one of its chief defenders, was Moses ibn Ezra Poems in the Arabic form have been written in a number of major West African literary languages like Hausa and Fulfulde.
RUBY Ruby is corundum whose red coloring derives from chromium impurities, all other color varieties of this mineral species being referred to as sapphire.
The ruby color range includes pinkish, purplish, orangey and brownish red gems depending on the chromium and iron content. The trace mineral content tends to vary with the geologic formation which produced the ruby, so that original place adjectives, such as Burmese and Thai, have come, in later years, to be sometimes used in describing color.
The stone below is an example of a corundum gem that some would call a ruby and for which some, more conservatively. The old saying about questionable stones goes: Unless the seller specifically states the stone is unheated you should assume that some kind of heat treatment has been used. Generally, high temperature heating and controlled cooling is done to clarify the stones, especially by dissolving "silk" rutile ; but it can also improve tone and saturation of color.
Such treatments can only be detected in stones whose residual inclusions, or surfaces, show signs of heat stress; so completely flawless stones will give no clues, and cannot be positively verified as unheated. The general view at present seems to be that simple heating, being indistinguishable from Nature's own heating processes, and stable, is acceptable: For this reason such enhancement does not radically lower the value of ruby gems.
Not so for gems treated with traditional dyeing red ruby oil or other, more recently invented, treatments such as surface or lattice diffusion, or glass infilling. With the possible exception of some of the latest diffusion processes routine gemological tests can detect the treatments.
Synthetics and Simulants Corundum was first synthesized in the early 's by a simple flame fusion process. Many jewelers and gemologists have had the unpleasant task of telling a proud heir that Grandmother's treasured ruby ring or brooch contains a synthetic flame fusion stone and has a lot more sentimental than commercial value.
These stones are both the easiest to identify and the least expensive to produce. Such stones often show diagnostic growth features called "curved striae", never seen in natural gemstones.
More complex processes have been developed in recent years such as flux melting and hydrothermal synthesis. These so closely simulate natural formation conditions that colors, and even inclusions, look extremely natural, and such stones are difficult for all but the most highly skilled professionals to identify as man-made.
Luckily there are several diagnostic inclusions such as "fingerprints" which identify a gem as natural ruby, and others which in many cases, can provide evidence for or against heating. Ruby simulants are many and varied including natural gems such as red spinel, rubellite tourmaline and garnet, and man made or enhanced materials like glass and dyed quartz.
Historically, various assembled stones such as garnet and glass doublets have been used as well. Of course, a heavily included or fractured stone will be less stable. For reasonably clean stones, no special wear or care precautions are necessary.
Ruby shows pleochroism, which means that the color varies with the direction of viewing. Gemologists use a simple tool called a dichroscope to test for this property, which will easily discriminate ruby from its natural simulants like red spinel, garnet and also from glass.
Most rubies show distinct purplish red and orangey red colors pleochroic colors, and the dichroscope displays them side by side for easy comparison.
In addition many rubies will fluoresce in long or short wave UV and this property can often be used to help identify a stone's geographic origin. Burmese rubies often fluoresce so strongly that the effect is noticeable even in sunlight.
Such stones seem literally to glow, and are greatly admired. Thai and African stones generally lack this property due to their higher iron content. Although Asia has historically been the major producer of ruby gems, there are many other sources including the USA, Australia and most recently Madagascar.
The silk which is so common in corundum can, if sufficiently abundant and precisely arranged, lead to asterism which with proper cutting, creates star rubies.
Today there are heating and diffusion processes which can increase the rutile content and improve such gems.The History of Makeup. Topics: Cosmetics, Practice Essay Samual Brown How accurate is it to suggest that the Treaty of Versailles was mainly responsible for the political and economic instability in Germany ?The political effects of the Weimar republic were as follows, that the Versailles diktat was “a blow in the face” to.
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