Crystals: Since the internal organization of mineral solids is so orderly, there should be, and frequently is, some external evidence of this order. If the solid crystal grows without external interference it will end up with flat, shiny surfaces, or crystal faces, that are parallel to layers of atoms within. It is even possible, by measurement of the angles which these external faces make with each other, to learn something of the atomic arrangement within. This is the business of the crystallographer. Since gem material is usually of high purity and has normally formed under ideal conditions in the earth, it is often found in transparent, well-formed crystals with good external faces. Often they are so well formed with regular, shiny faces that they give the impression of having already been cut and polished as gems. In size they may vary from microscopic individuals up to single crystal monsters weighing several tons each. Good, clear, clean, gem-stone crystals, except for quartz, seldom are found in large sizes.
All solids, with minor exceptions, have orderly internal atomic arrangements and so are classed as crystals. The modern crystallographer studies these arrangements by using specialized X-ray techniques. Also, less frequently, he will study the morphology or external shape and symmetry of these crystals. The science has advanced to the point where it is possible to determine just which kinds of patterns and symmetries may occur in natural and man-made crystals. All crystals, it has been discovered, can conveniently and logically be divided into thirty-two different kinds of symmetry groups or crystal classes.
For the sake of further convenience and simplification, it is possible to group these thirty-two classes into six crystal systems, all classes in a given system having some important symmetry in common. The systems are: isometric, tetragonal, ortho-rhombic, monoclinic, triclinic, and hexagonal. The gem minerals can often be identified and distinguished from each other by the crystal systems into which they fall as they grow according to the dictates of their atomic structures. Beryl, in all its varieties such as emerald and aquamarine, is hexagonal, as is corundum with its varieties ruby and sapphire. Spinel is isometric, like diamond rings and garnet, while topaz is orthorhombic and zircon is tetragonal. Everything that a gemstone rings is, how it looks, how it wears, and how it takes cutting and polishing, depends directly on its chemical composition and its internal structure. What a gemstone's characteristics are and how they arise makes an interesting study.
Sunday, August 17, 2008
Thursday, August 7, 2008
Light Characteristics
Light is easier to understand in terms of what it does than of what it is. The things it does are about as varied as the things it touches. Each substance has its own unique composition and structure, and handles light in a difway. When the word light is used it y means visible light. Visible light is ly only a very small part of the total y which is of a type known as electromag-radiation. Solid substances have an effect of this electromagnetic radiation. Their julation of visible light is of greater in when dealing with gemstones. Some the reaction between gemstones and ; light produces phenomenal and often full or exotic results. Some of these i will be discussed here are color, schiller, >m and chatoyancy, fire, and fluorescence.
color: Color, or perhaps even its absence, sn the most striking characteristic of a one. Basically, the color of a solid object ids on how it absorbs, transmits, or re-the various wavelengths or colors of light Lich it is exposed. "White" light is com-of a whole series of wavelengths or colors. 1 it strikes a solid object some of the colors be absorbed by the atomic structure as I energy. If this absorbed energy is con-1 to heat and then dissipated it is, in , lost to the observer. However, there is possibility that it will be converted to a ent visible wavelength and passed on . Assuming that some of it is absorbed, or all of the remaining wavelengths are :ed or reflected at the surface and come to the observer as something other than :, because some wavelengths have been acted from the original. Perhaps some or ill travel through the gemstone or diamond wedding bands instead of eye. If all wavelengths are absorbed, no light is reflected or transmitted and the solid looks black. If all are partially absorbed in an equal amount, the stone reflects or transmits gray.
color: Color, or perhaps even its absence, sn the most striking characteristic of a one. Basically, the color of a solid object ids on how it absorbs, transmits, or re-the various wavelengths or colors of light Lich it is exposed. "White" light is com-of a whole series of wavelengths or colors. 1 it strikes a solid object some of the colors be absorbed by the atomic structure as I energy. If this absorbed energy is con-1 to heat and then dissipated it is, in , lost to the observer. However, there is possibility that it will be converted to a ent visible wavelength and passed on . Assuming that some of it is absorbed, or all of the remaining wavelengths are :ed or reflected at the surface and come to the observer as something other than :, because some wavelengths have been acted from the original. Perhaps some or ill travel through the gemstone or diamond wedding bands instead of eye. If all wavelengths are absorbed, no light is reflected or transmitted and the solid looks black. If all are partially absorbed in an equal amount, the stone reflects or transmits gray.
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