Hi,does anyone know of any articles on here or elsewhere that help you learn how to use refractometers?I have received the gem kit for test 4 and have a microscope and am about to get a loupe.Im still saving for a refractometer.Where can you buy the RI liquid from?Also what are the other essential bits of testing equipment i need,ie the minimum as i have a very low budget.
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In USA you can try: http://www.kassoy.com/prodcat/Refractometers.asp
In GB, https://gem-a.com/gem-a-shop (download the catalogue)
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If you are on a tight budget
If you are on a tight budget, one of the Chinese refractometers sold on ebay for about $100 will work.Just get a return privilege and test out its accuracy on a piece of quartz, because not all of them are calibrated correctly.If the liquid does not come with it., the 1.8 liquid from ebay is a little less toxic than the 1.81 stuff and about as good.
For other instruments, I’d first suggest getting a copy of Hanneman’s book, Affordabe Gemology, as it will teach you more than most other books and allow you to access some really affordable solutions.You can buy a cheap dichroscope and a flashlight polariscope from ebay, too. You may want a small diffraction grating spectroscope. Hanneman’s book will discuss a strainless sphere and quartz wedge substitute which will allow you to determine optic sign and character with the polariscope. A cheap digital scale will allow you to determine SG. That is pretty much all you need, although it is fun and useful to have a set of Hanneman’s filters for quick ID in parcels. If you had more to spend you could get a small portable UV light like the Raytech versalum, although I’m not sure it is made any more. Another worthwhile investment is a standard magnet for magnetic susceptibility tests (look on line for the site that discusses this.
So refractometer, $100. H’s book, $50. Polariscope, $30. Dichroscope, $30. Magnet, $10. Not sure about other prices, but you can look them up on ebay.
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Thanks for sharing these useful info to new member. Henry
Hi gemfreak.
The refractometer is one of the most important instruments in gem identification. The Chinese ones work fine and as royjohn said, check the accuracy. It may be calibrated slightly off so just compensate for it. Quartz is Doubly Refractive and you should get readings of 1.544 to 1.553 DR. The birefringence is then 0.009 and is very consistent with quartz. If you are calibrated so quartz reads 1.540 to 1.549 it still has the correct birefringence of 0.009. So then just remember the calibration is low by 0.004 and add that back in. What’s most important is the birefringence of the gems. Like this example, quartz is 0.009 regardless of the calibration being slightly low. I have two of the Chinese refractometers that work fine. Keep in mind a refractometer can be quite frustrating to use while you are learning it. Keep at it and you will figure it out. A basic equipment list would include: Refractometer (a must have), loupe, polariscope, microscope, dichroscope, spectroscope ( get a student spectroscope. it is bigger and easier to use than a pocket spectroscope), gem cloth, Chelsea filter, pen light, tweezers ( I have maybe 10 to find one I like), Short wave fluorescent flashlight, daylight lighting. There are lots of additional tools but these are a good start. It takes a lot of work and knowledge to use these properly. It’s also a lot of fun.
Best wishes for you.
Roger
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Hi Roger, Nice to know we agree on refractometers, more or less. Add to instruments a digital scale for sg measurements with a small salad dressing cup and a thread or piece of fishing line. When I am back at my keyboard I will post how to do the sg with the little digital scales Another great thing to have is a copy of geology pro software, since you input the data you have and get out an answer or list of possibilities.
Royjohn