International Gem Society
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AN INTRODUCTION TO GEMOLOGY
by Don Clark CSM
...Gemology is the study of gemstones. Some dictionaries define it as the “scientific study of gemstones,” but it is almost impossible to remove the scientific element. There may be investors whose only interest is in the value of the stones, but if they ever need to distinguish one gem from another, they are dealing with science.
... There are many categories of gemologists. For the jeweler it is a key element of their business. They need to be able to answer their customer’s questions and identify the gems brought into them.
... The gold smith needs specific knowledge about the physical characteristics of gems. A setting that would be ideal for a diamond would be inappropriate for an opal and vice versa. The amount of pressure used to set the prongs on a garnet would break a tanzanite.
... Some gems will withstand the heat of repair work that involves high temperature soldering. Some can be left in the setting if steps are taken to moderate the amount of heat they receive. Still others are so heat sensitive they need to be removed.
... The lapidary also needs special knowledge. Cutting and polishing techniques vary from gem to gem. What would work well for one material would be a waste of time on another and disastrous on something else.
... When faceting thought needs to be given to color management. How the rough is oriented can make a lot of difference in the appearance of the finished gem. The style of cutting is also a part of color management. The choice of cut can lighten or darken a gem which will have considerable effect in both the appearance and the value of the stone.
... The choice of a cut, which includes the shape, number and location of facets, also influences the brilliance of the gem. The angles the facets are cut at have to be carefully chosen. Then these factors are balanced, or compromises made, so as to not sacrifice too much material in the pursuit of beauty.
... Another category of gemologist are the scientists. These are people with degrees in geology, chemistry and sometimes physics. While one of the smallest categories of gemologists, they are at the same time one of the most influential.
... At the heart of gemology is gem identification. Some rubies and garnets are impossible to tell apart from each other by observation, but their values are considerably different. A precise and accurate means to tell them apart is absolutely necessary.
... When dealing with whole crystals, the ruby and garnet are easy to distinguish. Garnets form in the cubic system. While they vary in shape, they tend to be roundish and the number of sides is always a multiple of four. Rubies on the other hand, form long thin crystals. They are in the hexagonal system and always have six sides.
... Most of the material that gets cut into gems isn’t found in whole crystals, but in broken pieces. Using the techniques of mineralogy, they are easily distinguished from each other. Scratch tests, where the unknown is scratched by various substances, will determine its hardness. Other useful tests are the reaction to acids and the flame of a blow torch. These are categorized as destructive tests and are obviously inappropriate for cut gems.
... For centuries it was the lapidary who was in a position to most easily recognize the differences in like appearing gems. During the cutting process gems get viewed intently, a perspective that no other gemologist has. Identifying inclusions are given a lot of attention, then as many as possible removed. Differences in hardness are readily apparent when cutting and polishing, as are other characteristics.
... A method needed to be devised where cut gems could be identified without damage. To this end scientists began to first, identify the measurable physical and optical properties of our gems. Next they devised instruments to measure these properties. There was a long process of systematically measuring and recording these properties so they could be looked up. (Though well established, this is actually an ongoing process.) Eventually all this got put together into methods that could be used by people without extensive scientific backgrounds or large and expensive laboratory equipment.
... That is not to say that it doesn’t require substantial education to identify gems. It is a large and complex subject that is continuing to increase in complexity as new gems are discovered and new ones are created in the laboratory. However, one doesn’t need a degree in chemistry or physics to simply measure the properties of our gems. The most esoteric part was discovering those properties and creating the tools to measure them.
... If you are interested in learning about gems the first step would be to learn how they are categorized. Also important in the early stages is learning the terminology used to describe gems. Next you can learn what the physical and optical properties are. When you have this background, you can get into gem identification.
... Of course there are many side roads to travel. You may find a fascination with phenomenal gems or their inclusions. Many people find a desire to collect gems and this often leads to making jewelry or learning how to cut gems.
... Whether your interest is casual or professional, there is much to delight and amaze. It is something you can do from your desk, or something that allows you to get your hands dirty. Plus the subject of gemology is one of those where you will never run out of new elements to discover.
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