6. Hydrostatic Scale or SG Heavy Liquids - Either of these tools can be used to measure the specific gravity of a gem material. This refers to the density of a gemstone compared to an equal volume of water. Some stones with a higher specific gravity will look smaller than others of a lower specific gravity, even when both may have the same carat weight value. Most laboratory set ups these days seem to prefer the hydrostatic scale. This useful instrument is actually an attachment system set-up composed of an electronic scale, beaker of water and thin wire basket.
7. Spectroscope - If you are familiar with how the human eye can see color, then the spectroscope is actually quite easy to understand. For the basic idea, any object that light touches may "selectively absorb" some certain wavelengths of the white light. Each wavelength range corresponds to a color, and so when light gets reflected off of the object and travels into our eyes, we see that object possessing a certain hue of color. Now, what a spectroscope does, is it allows you to see which wavelengths (or color ranges) are absorbed by a gemstone or mineral when light travels through it. This valuable information can sometimes even tell us the source element that creates the color in a gemstone (with more gemological knowledge of course).
8. Dichroscope - Some gemstones that are doubly refractive, can also show pleochroism. This means that they can appear to simultaneously show multiple hues of color when viewed. These stones can either be classified as dichromatic (2 colors) or trichromatic (3 colors). We use an instrument called the dichroscope to view two of these colors side by side and assess them individually. This can help separate some species that are known to be pleochroic from other non-pleochroic gems of the same color.
9. Masterstones or Color Grading Set - We know that the value of a gem is often tied to the presence or absence of vibrant color. For colorless and near-colorless diamonds, gemologists use a masterstone set to compare and judge the intensity of any color present. This set is usually composed of at least 3-5 stones that have been specifically calibrated / chosen to showcase certain levels of color that correspond to standard 'letter grades' that are frequently used in the industry by gemological laboratories.
10. Colored Filters - Some gemologists use colored filters such as the "chelsea filter" to different certain species of gems that look alike (such as aquamarine and blue topaz), however these are often used only as supportive or secondary tests, as the others are usually more consistent and dependable.
Gemological Equipment Should Always Be Used By Professionals in the Field, to Avoid Misinterpreting Results, Item Damage, and Confusions.
There are other laboratory instruments that are used in the industry today, such as spectrometers, x-ray machines, ultraviolet lamps and electronic scales. Each of these can significantly aid in the detective-work of gemologists as they help jewellers and traders to identify and/or separate the different products in their inventory.
2015 - Photography from the Gemological Institute of America
