What Type Of Loupe Should Be Used To Examine A Diamond?

May 14, 2017 – Posted in: Jewelry Blog

Loupes are used in all sorts of industries to examine all sorts of products. Printers of all kinds, art historians and collectors, watchmakers, surgeons, modeling enthusiasts, and many more. Oh, and jewelers and diamonds, of course.

Public Perception of Loupes

Which Loupe To Buy

In short, anybody who has a need to examine small details on any kind of surface or item will have use for a loupe but, as with men, not all loupes are created equal. Given that jewelers are looking for a variety of things when they use a loupe, all of which will be used to value the item, it’s important to get one that is appropriate to the task in hand.

The movie interpretation of a jeweler is usually set somewhere in a dark backstreet office with a very unofficial-looking man who has a half-smoked cigarette in one hand and a diamond in the other. To finish the ensemble he usually has a small micro-telescope wedged into an eye-socket. Take the backstreet and the cigarette out of the scene and examining precious stones hasn’t actually changed all that much since the heyday of film noir. All gem grading, including diamonds, of course, is still done by eye.

Why a Loupe is Important?

A jeweler examining an emerald cut diamond ring with a jewelers loupe
A jeweler examining one of our diamond ring with a jewelers loupe. Shop our Diamond Ring Collection.

This makes the right loupe the only way to get it absolutely right. Some aspects of determining the Four Cs – Color, Clarity, Cut and Carat – can be done by eye or, in the case of the carat weight, with jeweler’s scales. As an example, certain inclusions or flaws within the diamond may be quite visible to a trained eye, and color can also be detected up or (down) to a certain point but, if you don’t have that trained eye, a loupe is the only way to go. So what do you need to look at in terms of style, price, and quality?

Loupe Styles

Belomo Loupe

The most common – if not only – type of loupe used by jewelers to inspect diamonds is of the monocular variety. Not the monocles you see stuffy old English gentlemen using to peer at their butler through, however, although the basic principal is the same. Instead, you will need a loupe that more resembles a magnifying glass you may have had as a child, where the lens was able to pivot in and out of a plastic sleeve.

Also, at least as far as jewelers are concerned, you’ll rarely find loupes nowadays that are wedged against the eye, and the majority are simply held up to the eye when in use. By having the lens pivot back into an incorporated sleeve or case, it significantly reduces the risk of scratches or other damage to the lens. A loupe with scratches is next to useless as it will cause blurring, refraction and may mask the very things you are looking for.

Loupes also come in several magnification strengths. There are several physical limitations to what can be achieved with glass and the amount of magnification it can handle before the quality of the image starts to decrease rapidly. Unless manufacturing standards are seriously efficient and well-controlled, a 10X magnification rate is about the higher limit before quality starts to be traded off for the increased magnification. There are 20X and 30X loupes available, but most aren’t worth the money unless produced by one of very few high-end manufacturers.

Because of the limits of the physics in loupe manufacture and performance, the Federal Trade Commission insist that all gem grading is done with a 10X loupe, no more and no less. They state that, if a flaw cannot be detected with a 10X loupe, then it cannot be considered for valuation purposes.

What Loupes do Jewelers Use?

We’ve been talking about what consumers tend to use when examining jewelry, but these principles may not apply to jewelers.

Jewelers will have different loupes depending on what they are purchasing. If they are examining diamonds (or any stone), they will probably use both a 30x loupe and a 10x loupe. They will only judge the diamond based on the 10x loupe, but the 30x loupe will help them locate the inclusions that need inspection.

When examining jewelry (and not diamonds), they will always use a 10x loupe.

Price and Quality

Examining Jewelry with a Loupe

You can get a 10X loupe for a few dollars, but it won’t even be worth the small amount you paid for it. The best loupes are called Triplets, indicating that there are 3 lens elements used in the manufacture. This helps to improve the focus and reduces chromatic aberration (CA). CA is where light is refracted as it passes through objects – in this case glass – and isn’t focused properly as it hits the eye. The effect is purple fringing on one side of the diamond which then affects the whole image. Cheaper photography lenses often have CA issues, and manufacturers struggle to eliminate it completely.

Doublets (2 lenses) loupes are available, and many are good quality. However, a relatively small jump in price to a Triplet is usually well worth the investment.

Two of the biggest manufacturers of high quality Loupes are Nikon and Zeiss, both also renowned as high quality cameras, lens, and laboratory equipment. This means their products come with a premium attached for the consistent quality items they produce. A 10X loupe from either is likely to cost anywhere between $60 – $100, although pre-owned loupes are often available even on sites like eBay and Amazon.

An alternative manufacturer, but another with an excellent record in producing high-end optical equipment is Baush and Lomb. If you wear contact lenses, you may be more familiar with the name from there, as they are a very popular brand for both the lenses and the cleaning solution used to keep them in top condition. With B+L, you can expect to save about ? over the price of loupes from Nikon or Zeiss. Other than that, you may well fall prey to the principle of “buy cheap, buy twice” when you realize the budget model you bought really doesn’t cut it.


A 10X loupe from a reputable manufacturer will always be the sensible option. If you’re serious about diamonds and what makes them the grades they are, then a decent loupe is good value when you consider it doesn’t even reach the level of a single dinner at a half-decent restaurant.

The next thing you need to do is learn how to use it. Study what you need to be looking for, and you’ll find it’s not quite so easy as those who have been in the industry for many years will make it look.

Once you have your loupe, look after it. The time will come when you realize it’ll come in very handy for a non-diamond inspection, and you’ll realize it was worth passing up a nice piece of steak for.