A smooth, glass-like surface is the sign of a perfect polish. You may see pits or scratches. However, if they are few and invisible without magnification, they’ll have little effect on the beauty of the gem.

When observing gemstones through a microscope, it is normal to use gemological tweezers. These tweezers can be attached to the microscope itself or to an external support. While it is important to use tweezers instead of your fingers because your…

The crossed filters technique, not to be confused with the polarized crossed filters technique, is based on the emission of white light that is filtered by a blue medium. This filtered light, which is now blue, illuminates a gemstone that is…

One of the first problems student gemologists encounter is one advanced gemologists also face: high equipment costs. The variety and prices of modern gemology tools make them almost cost prohibitive for a hobbyist or someone not willing to make the…

The optical spectrum of a gemstone may be extremely useful in identification or in distinguishing between two gemstones that look alike, which is why optical properties are often mentioned in gemstone articles. The primary tool used to determine…

Step 3: Practical Gemology Lesson 1 Back to syllabus A dichroscope is one of the most useful instruments a gemologist can have. Its primary purpose is to determine the pleochroism of a gem. This can be a valuable piece of…

Step 3: Practical Gemology Lesson 2 Back to syllabus The microscope is an essential piece of lab instrument because it reveals inclusions that are the key to identifying some gems. Inclusions and color banding are often the…

Step 3: Practical Gemology Lesson 3 Back to syllabus Selective AbsorptionNatural, white light contains all the hues of the rainbow. Colored stones absorb some of the light that passes through them, or it is reflected from their…

Step 3: Practical Gemology Lesson 12 Back to syllabus The polariscope is one of gemology’s simplest and most useful tools. With a little practice and our three-part polariscope guide, you’ll soon be able to conduct some…

Step 3: Practical Gemology Lesson 13 Back to syllabus Testing for optic figure and sign is an important technique for gemstone identification. You’ll need a polariscope and a condensing sphere. If your polariscope doesn’t have…

Step 3: Practical Gemology Lesson 14 Back to syllabus A gemologist can conduct many different tests with a polariscope. Gemstone twinning, dichroism, and internal crystal strain are some of the physical and optical characteristics…

Step 4: Gem Grading Lesson 11 Back to syllabus What is a Reticle? A reticle (réttik’l) is an optical device used in conjunction with a magnifying lens. For example, the cross hairs on a gun sight are a type of reticle….

Step 3: Practical Gemology Lesson 15 Back to syllabus The thought of grading and identifying gems may seem truly daunting for beginners. Tools can be expensive and setting up a laboratory sounds like something best reserved for…

Although based on sophisticated science, the spectroscope itself is a simple device that needs only a few adjustments to use. All models have ways of adjusting the focus and the amount of light entering the instrument. Advanced models also have ways…

For decades, the only refractometer I used was a Gem Instruments, Duplex II. This is regarded as the best available in the US. In Europe, the Rayner’s are considered best. Shipping costs prohibit these from being regularly traded across the…

A couple years ago, I wrote a scathing review about some inexpensive refractometers that had appeared on eBay. The units were not particularly accurate and were not suitable for spot readings. The worst part, and what got them such a terrible…

Authoritative gemological encyclopedias and charts don’t have to be restricted to print. Interactive media can put vast amounts of information at the click of a mouse (or the tap of a finger) for professional gemologists and novice gem collectors…

Inexpensive, no-name-brand, Chinese made refractometers have recently appeared on eBay for around $150. With most refractometers ranging between $550 and $1000, that is highly appealing! I know that excellent optical equipment is coming from…

Polariscopes are one of our most useful instruments. They come in a wide variety of prices and qualities. A new Gem Instrument’s polariscope costs close to $400 with shipping. The simplest polariscope is made by laying a $1 filter on top of a…

Finally there is a professional set of software for the gemologist! Gemology Tools is a set of programs designed specifically for the appraiser. It will help you with your identification, estimating gem weight, organizing your information, as well…

Spectroscopes are one of the most difficult gem instruments to master. They come in two varieties: prism and diffraction grating. There is no clear preference between the two, as each has its advantages and disadvantages. Diffraction grating…

There is a new piece of software available that will be of interest to many of you. It is called the Diamond Calculator. While it was designed specifically to simplify the diamond appraising, it has many other uses as well. The Diamond Calculator…

Achiever Microscope $259 + $10 Shipping GreatScopes P.O. Box 1948 Jamestown, NC 27282 www.greatscopes.com (336) 454-6361 Achiever MicroscopeFeatures: • Dual 10x wide field eyepieces, fully adjustable for both children and adults to look…

Step 3: Practical Gemology Lesson 4 Back to syllabus Gemstone identification is like detective work. You gather clues and eliminate suspects until you’re left with clues that lead to only one suspect … or gemstone. Since few gems…

The Gemological Institute of America (GIA) used to offer plastic color masters for color grading. They argued that the plastic “gems” gave a more realistic representation of color than any flat media could. Unfortunately, the company making…

Whether you’re appraising an exotic gemstone or just starting a gem collection, you need gemology reference books to help you analyze and identify gemstones. Our review covers four works essential for your gemology library. Gemstones of the…

Artists, lapidaries, and gem merchants all have stories to tell. Three very different books with varied perspectives explore the lives of people who work with gems. Our gemology book reviews may give you some insight into what it takes to carve a…

Gemologists must often evaluate diamond symmetry. For a rigorous evaluation, you will need a device called a proportionscope, which allows you to project the image of the diamond onto a screen to measure lengths and angles. This device has two…

Step 3: Practical Gemology Lesson 5 Back to syllabus You can use a refractometer to determine the refractive indexes of most cabochons and carved gems. If your test gems have a flat, polished bottom, you can test them as you would…

Step 3: Practical Gemology Lesson 6 Back to syllabus Optic character is another useful clue in gem identification. This property exists in every doubly refractive gem but not in singly refractive or amorphous materials. The optic…

Genesis and Classification of Agates and Jaspers: a New Theory. Marco Campos-Venuti. Rome, Italy: Tophgrafia Luciani, 2012. 160 pp. When talking with gemologists and jewelers, the topic eventually moves away from precious gems to agate and jasper…

Faceting Articles, Designs, & Pictures. Glenn Klein. I purchased Glenn Klein’s new book, Faceting Articles, Designs, & Pictures, in anticipation of reading it during my summer excursion to upper Ontario where I spend a week fishing,…

The Collector’s Guide to the Minerals of New York State. Dr. Steven C. Chamberlain and Dr. George W. Robinson. Atglen, Pennsylvania: Schiffer Publishing, Ltd. 2013. 96 pp. In writing The Collector’s Guide to the Minerals of New York State,…

If you’ve made it through our 3-part refractometer guide for gemologists, test your knowledge of refractive index (RI) analysis with this mini-quiz. Click on the link at the end of the quiz to see the correct answers. Got some wrong? Check out…

Amateur Gemstone Faceting Volume 1: The Essentials. Tom Herbst. Facetable Books. 2014. 428 pp. Amateur gemstone faceter Tom Herbst begins his new faceting book with an explanation. He decided to write his book for two main reasons: Finding…