Gemstone Microscope and Its Usage

The function of the microscope is to develop objects so as to make them more surely descriptive to the human eye. Its use in science is unlimited, and to the gemologist the microscope is more important than any other instrument. This is because one of the biggest problems in contemporary jewelry is the detection of synthetic and imitation stones, and without a microscope the task would be roughly impossible.

The detection of imitation stones covers a vast field and the following lines serve only as an introduction. Three out of four of the most valued gem stones can be produced synthetically in the laboratory. These are the ruby, the sapphire, and the emerald. Needless to say, the difference in value between a natural and synthetic stone is enormous, and it is therefore of most significance to the jeweler that he can be sure they can be effectively considerable from each other.

Microscope

Synthetic rubies made by the flame-fusion process are in all their physical properties roughly identical with the natural stone. Chemically, both are crystalline aluminum oxide. The red color is in both cases produced by minuscule quantities of chromic oxide, and if synthetic and natural rubies are tested for their definite gravity, refractive index, and absorption spectra, the same results occur in both cases. Yet, if they are settled under a microscope, a marked difference between the two is found. What then are these internal telltale features that will enable us to distinguish the real from the synthetic?

Fine curved lines are immediately noticeable that are rather like the grooves of a phonograph narrative and run straight through the stone. There are also some black spots interspersed irregularly throughout the gem. The curved lines are known as growth lines, and they are produced while the formation of the synthetic boule and are a positive sign that the stone is synthetic. The black spots narrate tiny bubbles of gas, and these, too, were included in the boule while its formation. Gas bubbles and curved growth lines are therefore typical characteristics of synthetic corundum.

But, what does the inside of natural corundum look like under the microscope? Again, there are the curved growth lines in the synthetic stone, but, in the natural one, the growth lines are straight and set at definite angles. This latter feature is an important characteristic of most natural mineral crystals. The microscope can furnish all-important clues in the identification of rubies and sapphires.

A gem stone that may set an even bigger problem is the emerald. In this case, synthetic stones are internally also remarkably similar to the natural ones. Fortunately, Chatham's synthetic emeralds do have a lower definite gravity and refractive index than the natural stones, but it is not all the time possible, if a stone is set in a piece of jewelry, to apply these tests. Here the microscope is beneficial again.

Natural emerald possesses cer¬tain internal features called inclusions. Some of them take the form of spiky cavities filled with tiny mineral crystals and gas bubbles. Indeed, they are so typical that they can be linked with definite mining localities and thus form an important guide to the origin of some emeralds. Chatham's synthetic emeralds also possess extra inclusions, and under the micro¬scope, these look rather like a fine pattern of lace. They surely consist of minuscule interweaving channels filled with liquid and thus are very distinct in character from the inclusions of the natural emeralds.

A simple magnifying glass that enlarges ten times can also be a critical aid in the identification of some gem stones. Thus, a colorless zircon might well be confused with a real diamond, but if both are carefully examined with a hand lens by seeing straight through the top of the stone at the rear facets, everything at the back of the zircon will appear double, thus revealing its strong light-splitting property.

Since a brilliant belongs to the cubic crystal system, letting light rays pass straight through without splitting them, the double image will not be shown by it. This is one simple test that immediately distinguishes between these two gem stones. There is one direction along the so-called optic axis of a double-refractive stone where the light rays are not split and the doubling effect cannot be seen. It is therefore wise to tilt the gem a minuscule when examining it with a lens to insure that the optic axis does not lie at right angles to the table facet.

Gemstone Microscope and Its Usage

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