ARCUS diamond tester (also tests Moissanite, ruby, sapphire) - by Gemtrue

Summary

NOW AVAILABLE!

New as of Christmas 2025. The ARCUS is absolutely the most accurate of the low-cost* diamond tester; it is the only 'simple' tester that isn't fooled by our own selection of 'difficult' stones. This is due to its exceptional built-in UV light which detects the latest low-conductivity Moissanites; most* other testers show these Moissanites to be 'diamond'. 

* all testers, excluding the specialist synthetic-diamond testers which cost between £750.00 and £1000.00.

• Tests for diamond and Moissanite and ruby/sapphire.
• The top of the tester lights up with the name of the stone (and a different colour for each). 
  
• Guarantee, 1 year.

Every diamond tester ever made has its limitations. For standard diamond testing see our article Guide to Buying Diamond Testers. None of these can distinguish natural (mined) diamonds from synthetic (lab-grown) diamonds, both are diamond - for these you will require a specialist tester, see Testing for Synthetic Diamonds. Synthetic is not to be confused with simulant which is "anything you may think looks like diamond even though it isn't" - for which standard testers such as the ARCUS are designed. 

Technical

PHYSICAL

Dimensions: 7½ X 1 X 1½ inches (185 X 25 X 30mm)

Weight: 100g

Tip: can test stones down to 0.02ct (2pt) in size. 

Operating temperature: recommended between 18 and 27 degrees C (64 to 81 degrees F). Though tests show it works fine down to 15 degrees C. (59 degrees F).

RESPONSE TIME

Warm-up time when switched on: 15 to 20 seconds

Testing: result in 1 or 2 seconds

Warm-up time between tests: 2 or 3 seconds

POWER 

One PP3 battery (supplied).
Optional 9 volt power supply (mains adaptor)

Battery life: don't know, a few thousand tests?

Low-battery indicator: none, when it fails to warm up, it needs a new battery

Auto-shut-off: yes, it bleeps then turns itself off if not used for five minutes.

ACCESSORIES / PRESENTATION 

• fitted case
• carrying strap
• stone-holder
• polishing cloth (to remove any surface grease-free before testing)
• instructions
• unique system for recording the readings (no app. required): a note pad

RELIABILITY

For testing diamonds and Moissanite, estimate, you would get the correct result 95% of the time. This will change over the months and years as the manufacturers of Moissanite tweak the formula.

Disclaimer

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.

Alternatives

The testers below are to distinguish diamond from non-diamond (simulant/imitation); they do not include the very specialist testers that distinguish natural diamond from synthetic diamond, see the ARI, ARETE and APEX. "Synthetic" is a scientific term meaning 'made by man in a factory/laboratory to the same formula found in nature' (read all about it).

[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.  

Free gift details

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

	READING MAGNIFIER, 80X80mm WITH 4 L.E.D. LIGHTS [cl] (RRP £7.50 )
	Brilliant-cut cubic zirconia, 5mm diameter (RRP £5.90 )
	Stone grip (RRP £1.50 )