​​​​Diamond Grading 101

The first step in examining a diamond for clarity is obtaining the proper tools, which are a ten-power (10x) magnifier, locking tweezers, a lint free cloth, and an adequate light source such as an ordinary desk lamp with a daylight fluorescent bulb.

It will most likely be easier for you to view a diamond through a microscope. Many jewelry stores will have a microscope available for your use. However, not all jewelry stores own a microscope and others wouldn’t let you use it if they did. Nevertheless, most of our industry grades diamonds for clarity using a hand held ten power magnifier known as a “loupe” (pronounced loop) and you can to.

A loupe differs from a regular magnifying glass in that it is fully corrected which prevents objects from being distorted. When selecting or using a loupe, make sure that it is a fully corrected, ten power (10x), triplet loupe. Some stores will try and “pull a fast one” on you by slipping you a five or six power loupe… The construction of the loupes look the same, but they deliver completely different results, with half the magnification everything is going to look a whole lot better. Make sure that the loupe you are using has a 10x stamped on it somewhere.

Learning to use a loupe can be challenging and you may feel a bit foolish at first. It’s not going to help that every jeweler in town makes using a loupe look like no big deal. Realize that they’ve been doing it for a lot longer than you have and they’ve had years of practice. A good sales person will take the time to show you how to properly and effectively use a loupe.

I used to teach our customers to use a loupe in the following manner… If the loupe is closed, open it. Understand that the loupes we use for diamond grading are double corrected, so you may look through it from either direction and you may want to take your glasses off if you wear them. There is no right or wrong side of the lens to look through. Loop the index finger of your dominant hand through the opening of the loupe’s protective case. Hold the diamond ring or diamond mounted in tweezers in your opposite hand between your index finger and your thumb. Next place the three remaining fingers from each hand against each other to form a stationary base. At this point, the diamond and loupe should be about 1/2 – 1 inch away from each other. Sit upright with your elbows comfortably rested on a table, and bring your hands towards your face until the loupe is about 1 – 2 inches away from your eye. Keep your head up as if you were talking with a friend across the table. People have a natural tendency to hang their head over the loupe and tweezers (looking down at the table) which blocks out the light source preventing proper grading of the diamond.

Using a loupe may seem a little awkward at first, but with a little practice you will soon get the hang of it. We recommend that in the beginning you practice by looking at your fingerprints and fingernails. This accomplishes several things… First it will give you an appreciation for the degree of magnification that you are using and how minute a diamond’s flaws actually are. Secondly, it boosts your local economy in that it emphasizes the need for a good manicure.

Next comes my favorite part… Teaching you how to use diamond tweezers and watching your face when you squeeze the tweezers just a little to hard and the diamond pops out and flies across the room. It happens all the time, even to people who have been in the industry all of their lives, but lay-peoples reactions are classic. If you do shoot a diamond across the room, don’t panic just find it.

Diamond tweezers are quite different from the tweezers you use to remove a splinter or pluck your eyebrows. Most diamond tweezers measure about 6 inches in length and have a very fine tip that has a groove or rough finish on the inner edges to hold the diamond in place. Most retail jewelers use tweezers that are equipped with a slide lock that is supposed to hold the diamond in place and make it easier for you to inspect it.

The easiest way to secure a diamond in the tweezers is to hold the tweezers in your dominant hand between your thumb and middle finger. Place your index finger just inside of the tweezers opening exerting just enough pressure to open the tips slightly. Use the tweezers to flip the diamond on to it’s crown (top side of the diamond that faces you when it is mounted). Next, lower the tweezers around the diamond and gently move the slide forward (towards the tips) until it just barely catches. You are not tightening a nut on a bolt, use very little pressure. Exerting too much pressure can damage the girdle edge of the diamond! As with learning to use a loupe, this too will become easier with practice…

The purpose of using tweezers to hold a diamond has nothing to do with sterility, so don’t be afraid to pick up a diamond with your fingers because you can’t hurt it. However, if you do pick up a diamond with your fingers you will leave some oil and smudges that will look like tiny white pinpoints under magnification, so dip it in a little ethyl alcohol and wipe it dry with a lint free cloth to clean it before you grade it.

Once you have obtained the equipment necessary to grade a diamond, proceed as follows:

Clean the diamond by rubbing it with a lint free cloth. If necessary, soak it in ethyl alcohol or have it professionally steam cleaned by a jewelry store. Once the diamond is clean, mount it in a pair of diamond tweezers.

Examine the diamond from all angles with your eyes to determine whether any inclusions or blemishes are visible without magnification from the top of the stone. If you inspect a diamond with a loupe before grading it with your eyes, you are more likely to mis-grade the diamond because our eyes have a tendency to see what they expect to see. If you locate the inclusions under magnification and then inspect the diamond with your eyes you are more likely to imagine that you can see an inclusion regardless of whether it’s actually visible to the unaided eye.

Examine the diamond with a 10x loupe from all angles. Jewelry store clerks will frequently object when you inspect the underside of a diamond and tell you that all grading is based on the visibility of inclusions as inspected from the top of the stone. It’s true, but Ignore them and inspect the diamond from all angles to ensure that there are no chips on the underside of the stone. In addition, most laser and clarity treatments are difficult to detect from the topside of a diamond.

Note that for viewing inclusions, your light source should be situated so that light passes through the side of the diamond, and for viewing surface blemishes, it should reflect off the surface of the stone.


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