Digital refractometer by Presidium (model Prim II)
Digital refractometer by Presidium (model Prim II)
Digital refractometer by Presidium (model Prim II)
Digital refractometer by Presidium (model Prim II)
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  • Load image into Gallery viewer, Digital refractometer by Presidium (model Prim II)
  • Load image into Gallery viewer, Digital refractometer by Presidium (model Prim II)
  • Load image into Gallery viewer, Digital refractometer by Presidium (model Prim II)

Digital refractometer by Presidium (model Prim II)

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(Single item price excluding VAT: £249.58)

Stock: Available

UK company, easy telephone support

Free gift option with this item

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Pickup available from Quicktest (WD18 8JA)
Email us or call on 01923-220206 for appointment.


Made by Presidium, the leading manufacturers of gem testing equipment.

There is downloadable software to connect it to your computer. The reading is then displayed along with a list of stones that match the reading, and you can click on each stone to see more information (constants). This saves time looking up charts.

Comes with a USB cable (connects to any computer/mobile device / USB-mains adaptor). 

Works with loose stones and also stones mounted in small items of jewellery.


- to confirm stones are as described by your supplier

- to show a customer the reading, when you already know what the stone is and just need to 'prove' it

- to sort parcels of stones to see which look 'interesting' and worthy of further investigation, and then... narrow the possibilities down to a handful of stones (sometimes just 1 or 2) so that you can carry out further investigations.

Guarantee: 1 year. 


Advantages, as an electronic tester:- instant reading and no waiting time between tests

- tiny sensor for testing stones down to 3mm diameter

- pull-out refractive index chart as a quick-reference for diamond / diamond simulants (including Moissanite) 

- built-in 8-piece gemstone holder (sets of sample gems are an optional extra)

- use the downloadable software [from Presidium], each test will display data on the computer listing many variables (in addition to refractive index) that will help you identify the stone.

Disadvantages, as an electronic tester:- although mounted stones can be tested, the item of jewellery must be placed over the sensor so that the top (table) of the stone covers the hole, and this is not possible with large or 'lumpy' items of jewellery

- will test loose stones only, not mounted stones

- the surface of the stone must be perfectly flat, perfectly polished and perfectly clean (i.e. most stones but not cabochons and beads)

- it is a sensitive piece of laboratory equipment, it must be kept clean and dry, the sensor must be kept dust-free, it must not be bumped in and out of bags or used on damp outside market stalls

- as with all testers, there are many stones with the same, or similar, readings

Advantages over an optical refractometer:- gives higher readings (1.00 to 3.00) and this enables it to test for diamond and for simulants such as Moissanite

- no contact fluid required

- fast and easy to use, easy-to-read digital display

- wider range of readings

Disadvantages over an optical refractometer:- it's not as versatile as an optical refractometer, you only get one reading for each stone (technical: you can't measure the birefringence).

- this Presidium "Digital refractometer" does measure refractive index but, technically, it is not a refractometer, it is a reflectivity meter that uses a clever computer program to calculate refractive index. You probably don't need to know that!  All you need to know is (if you are familiar with the optical refractometer) it does not show double refraction and so, for the expert, is not as flexible as an optical refractometer. 


Range of measurement, 1.000 to 3.000

Power: one 9 Volt battery + USB (cable supplied)

Size 5 X 3 X 2 inches (125X 75 X 50mm)

Item weight 150g. 


Have you seen the Fascinating article about gem testers? This will answer many questions about electronic gem testers (all electronic gem testers) - how 'reliable' are they? How 'easy to use' are they?

In summary: no gem tester will light up with a number (or name) that tells you, with 100% certainty, the name of the gemstone. This is because nature does not make gemstones to a standard formulae, there are always variations. All of gemmology is a detective game, starting with an idea of what the gemstone might be (that is what electronic gem testers are for) then using knowledge and skill to find the answer.

Alternative gem testers

Please note, none of these testers will distinguish natural stones from synthetic stones. "Synthetic" is a scientific term meaning 'made by man in a factory/laboratory to the same formula found in nature', the two are usually indistinguishable. 


Tests mounted stones [1]

Tests  Diamond

Tests  Moissanite

Ruby / 

Other stones

Handheld presidium gem tester (GEMTEST-PGI)

Shows up as diamond

31 stones

Standard Presidium (GEMTEST-P2)

Shows up as diamond

17 stones

Presidium Duo gem tester (GEMTEST-DUO-II)



Refractometer (optical not electronic) (Refract-L)

Hundreds of stones [4]

[1] All testers test loose stones but not all can test mounted (set in jewellery) stones.

[2] The probe / analogue meter will test mounted stones, the digital meter will only test loose stones.

[3] The probe / analogue meter: 17 stones; the digital meter: 40 stones.

[4] Skill and practice is required to use an optical refractometer, instructions are not included, see any textbook about gemmology…or the internet.   


All testers  must be used in conjunction with the user's skill, knowledge and experience. Under no circumstances shall QUICKTEST be liable for direct or indirect loss sustained in connection with any item. Nothing is 100% accurate, you must understand the limitations of any tester you buy. We also suggest you regularly test known samples to check for any obvious faults. Full support given for items you buy from QUICKTEST.


Free gift details

If you would like one of the following free gifts with this product, select one from “Select your free gift” above.

10X18 with 20X12 Loupe - not triplets (RRP £6.50 )

Diamond gauge, acrylic sheet (RRP £7.50 )

Light-Loupe, 4X with light (lightmag) (RRP £5.90 )


Ask a Question
  • can you use this for mounted stones


  • Please can I use this Digital refractometer by presidium ( Model prim 11) to test and know a real Rough Diamond from fake.

    No. The stone must have a perfectly polished perfectly flat surface to rest on the test-plate of the refractometer.