Back to IGS | FAQ | Contact

Portable Refractometers

A client sent me this link, I’ve never seen one of these, could it be used for gems?

Has anyone here used one of these?

And the follow up… Has anyone used ANY digital refractometers that work well?

With the sapphire prism the range is only 1.32 to 1.65, I can’t see those ones being of any use, unless I read it wrong :slight_smile:

1 Like

I didn’t even know that digital refractometers existed before today, yes, reading more about it, that’s fairly useless

I believe this type of refractometer is used more in the food industry–for liquids such as syrup and liquors.

1 Like

It’s used for measuring the amount of solids in a liquid or close to that, I used one before doing refrigeration work but they don’t work on gems.

1 Like

Yes, it’s for measuring sugar content in various juices, etc. Further, any kind of digital refractometer, while it WILL measure over the limit (1.80-1.81) stones, will not give you birefringence measurements or tell you the optic sign of the material. Ability to measure birefringence (or single refraction) and tell the optic sign are key add-ons to the simple measurement of RI that the refractometer gives you. So if you know your gemology, the simple desk refractometer is the best tool. You can supplement with a digital, but in my very limited experience with them, they just are not that reliable and exact in their readings. You need a well polished facet or they are off. With a poorly polished facet your desk refractometer will give a fainter reading, but it will be an accurate one if you can see the shadow. There are other ways to determine the identity of the few stones that are over the limit. -royjohn

1 Like

Yes, I have 3, and they all work very well. I have used a Gemeter90 for over 25 years, and it will read any RI from 1.20 to 3.00. My second is a Presidium unit also reads the same. And the third unit is Chinese in origin, but only reads to 1.85
I cross check between the units if I have a spurious reading, but 99% of the work is done on the Gemeter 90. All three are portable, simple to use and DO NOT REQUIRE A HAZARDOUS OR TOXIC FLUID…
The digital units are also less costly than the other type and only require a battery change twice a year.


Yes I have used Gem Eye. The trick is to really really clean the stones your testing. I have tested them against the GIA refractometer I typically use in my Lab. You have to know your stuff though just like with the GIA one. It will tell you the to choices of what your testing and give you the RI as well as other possibilities. It won’t tell you if it’s synthetic or heated/treated in any way but there are test for just that.