Gem refractometers – Buying guide & Comparison
If you don’t have the time to go through all the extensive documentation in the field of gemology and are just after a quick suggestion for a good gem refractometer to get you started then the following short paragraph should provide all the information you need. The gemkit3+book package was very well received by both beginner and experienced gemologists alike since it contains the most important tools to practice this hobby all gathered together in a convenient and surprisingly affordable package. The piece de resistance is the refractometer itself, certified to take readings from a 1,30 to 1,81 refraction index. Beginners will love this as a starter kit and experts will find it of great use as a portable, unpretentious unit. If you already have most of the items in the gemkit+ and only need the device itself and some RI fluid, then the Ade Advanced Optics ExtGemRefra will make for a good purchase.
Whether you’re out to buy the best gem refractometer available for sale to equip your geology lab or just a hobbyist or corner store jeweler, there are a few things you to know about the product before making your purchase. We’ve looked through the best gem refractometer reviews online to see what are the most common attributes amateurs and professionals alike take into account when making an evaluation and listed them below.
First, the basics
The refractometer is one of the most important gem testing instruments since it lets you know two very useful parameters for gem identification: the refraction index (RI) and the strength of the gem’s double refraction (birefringence).
The refraction index is usually different for every gem and makes for a pretty straightforward identification method. Only some gems have a double refraction, and by taking two measures from such a gem you can calculate the strength of its birefringence, which offers further data for identification. Of course, the fact that you can separate mono-refracting from bi-refracting gems is very useful as well.
Like any refractometer, the variety used in gemology works by focusing the refracted light from the sample into a scale. The readings are then taken by viewing the scale through a focusing lens. Unlike with portable types, the gem refractometer will need its own light source to function, most commonly a monochromatic LED light on recent models. This gives it a great advantage over a microscope because it allows it to take readings of opaque gems as well as transparent ones.
This is especially important for scientists and jewelers since a good deal of their respective jobs involve taking accurate readings. The best gemological refractometers used in labs generally have a far lower margin for error than it might be reasonably needed by a hobbyist using his or her library books for reference.
Enthusiasts and even most jewelers might want to favor other characteristics over this one, such as how durable, affordable and easy to carry the unit is, since the most common margins of error specified by manufacturers are generally well within the parameters required for them to do their work.
To ensure for the most accurate reading, it’s sometimes required to compensate for room temperature. Certain units do this automatically, which makes for great convenience since the user won’t have to consult various charts and then make the necessary adjustments by hand.
Before buying you should always consider what your needs from the meter are. Hobbyists and gemology beginner won’t need the highest specs model, and even specialists don’t feel too comfortable carrying their best refractometer on location.
Even more “affordable” refractometers can cost a pretty penny, but high-performance ones will really burn a hole in your pocket, so don’t get obsessive over specs when you aren’t in a position to benefit from them anyway.
Speaking of value for the dollar, make sure that you buy a sturdy, durable model, with a casing made out of metal rather than plastic.
In order for the refractometer to work properly, the gem must be placed over a layer of refracting oil, which needs to be rated for the maximum refraction index that the device measure (generally 1,81). Make sure that the manufacturer provides an adequate quantity of fluid with the meter, so you will be able to use it straight out of the box for testing.
A bag for easy carry will be especially important if you plan on using the refractometer on the go. The need for transport in the gemology world arises more often than most of us would expect, so a good bag might well prove its worth.
All models that come with an integrated light will also require batteries, and it’s always nice to have these included as well.
Top gem refractometer reviews in 2018
Containing a Chelsea filter, a dichroscope, a triplet jeweler’s loupe with 10x magnification and a gemological refractometer, this kit has everything to get a regular Joe started in gemology or to provide a highly convenient traveling kit for an expert in the field since it all fits in a discreet black case.
The meter can take accurate measurements of the refraction index between 1 and 1.80 units, enough for any task you might need it for. It also comes with its own LED light and batteries as well as 10 grams of RI 1,80 contact fluid.
The lenses are protected by a strong metal case while in use, and a nylon zip-lock back is provided for easy carriage.
The whole package received good ratings on retail sites for its quality but what impressed people the most was the very good value they received for a price slightly above that of a mid-range refractometer.
Buy from Amazon.com for ($183)
Ade Advanced Optics ExtGemRefra
The Nevada based Ade Advanced Optics seems to really have hit upon a gem with this product. It is both accurate, sturdy and contains some features not usually found in refractometers of its category.
The most salient of these is its automatic temperature compensation capability, which allows it to adjust for any climate within its operational range without the need for user input. This is especially convenient for gem hunters that need to carry a measuring tool to outdoors marketplaces or residential homes, where precise air temperature might sometimes be hard to determine.
The item is also easy to carry around, thanks to its low weight of just 0,8-0,9 lb and soft carry case. You won’t have to worry that much about dropping it since its thick glass optics and metal casing gives it good impact resistance.
The product also comes with its own RI oil rated at 1.80, a polarizing filter and a yellow monochromatic light, which would be difficult to find for sale otherwise.
Buy from Amazon.com for ($140.98)
Ade Advanced Optics GL500
The comparatively affordable GL500 is an even more portable unit than its premium cousin, the ExtGemRefra. While its functionality and features didn’t receive the same praise (but no complaints either) its light weight and sturdiness make it very suitable for a gemologist working out in the field and for gem hunters making their way from stand to stand through crowded marketplaces or conference halls.
Both these qualities are a result of its aluminum construction and built-in LED light, which eliminates the need for a flashlight or any other sort of outside illuminator that would otherwise be required to be carried separately.
The importance Ade Advanced Optics gave to portability when designing this product is further displayed by the available accessories they decided to include in the package: a polarizing filter and two different carrying cases, one soft and comfortable while the other one hard, to offer adequate protection from physical forces.
Buy from Amazon.com for ($89.99)
An overall good quality product, the TTG-181 offers all the functionality needed for the gemology enthusiast and jeweler alike. Its accuracy is specified by the manufacturer to be at 0,01 RI, which makes it sensitive enough to categorize almost every gem on the planet.
The range is equally suitable, between 1,30 and 1,81, covering every reference value you might find in a gemology catalog.
It’s got an integrated LED illuminator with an easy to access on and off switch and a polarizing filter, but you’ll need to shop for a bottle of 1,81 rated RI fluid since this doesn’t come in the package.
Portability is also good, with the item weighing in at only 0,88 lb and having its own carrying pouch. An instruction manual is also supplied by the manufacturer but the button cell batteries it requires to run are not.
Click to see the price on Amazon!
Losco Instrument GML-501
With an accuracy of 0,01 RI between the ranges of 1,30 and 1,81 RI this Losco Instrument product will make a good work aid for any scientist, jeweler and gemology enthusiast. Furthermore, it offers a similar degree of functionality as any other gem refractometer while not affecting your personal budget quite to the same degree.
Its affordability doesn’t take away from convenience either since you’ll go through the same usual motions while using it: Open the upper cover and wash the prism with alcohol.
Place just a drop of refracting oil and even it smoothly, so that the gem makes good contact with the glass. (the gem should be, of course, polished and smoothened out on its contact surface). Turn on the integrated light and adjust the focus on the eyepiece until the light/dark boundary appears clear on the scale. Mind that you
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