10X Loop - The Gemologists Best Friend

The simple hand- loops is the most valuable tool of the gemologist. You can learn more with it, and with greater ease, than any other instrument. Add to that the fact that it is your least expensive piece of equipment and it fits easily into a pocket, purse or briefcase and you begin to see why it is called, "the Gemologist Best Friend."

Loops come in several varieties. Watch makers prefer the kind that are held by the eye socket. There are loops that are worn like eyeglasses, or those that clip onto your glasses. Some are illuminated, have built in tweezers and other fancy features. For gem examination, the hand loop is preferred. 

10-power magnification is the most useful for our purposes. Above that the depth of field, the area that is in focus, is so small that they become hard to use. A microscope is the best tool for higher magnification. Lower powered magnification also has its place, but you can't see as much detail. So 10-power has become the standard for hand held gem examination.

One of the terms used to describe a loop is "triplet." That means that is has three lenses. This arrangement has no distortion around the edges. Another feature in a high-end loop is to give the lenses a special coating for "color correction." That means that the colors you see are natural and not distorted by passing the loop.

The standard for judging the quality of diamonds is what an expert can see in good lighting, with a 10X, color corrected, triplet loop. By usage, this has become the standard for- professional evaluation of colored stones as well. However, that doesn't mean you need an expensive loop for study. You can get as much information and enjoyment- from a less expensive model.

How to use a hand loupe

Using a loop gracefully takes a bit practice, but soon becomes second nature. When you open a loupe the cover becomes a handle. Slide your index finger through the opening and then rest your hand against your cheek. This is to steady the loop. Now you only have one hand to move for focusing. 

Before you focus on anything, consider the light around you. If you want to see the surface of the gem, to evaluate the cutting and polishing, you will want the light shining down on the stone. If you are in a room with an overhead light, this is simple. If your best light source is a window, you will need to position yourself so the light is coming over your shoulder. The most important thing is to avoid having your shadow on the stone.

To see the inclusions in a gem you need the light behind the stone and shining through it. Often you can get to see both the surface and the interior of the gem with a minimum of adjusting. These two conditions are almost always easy to achieve with a little thought. The only limitation is having too little light to see well.

To focus your loop, hold your loupe hand firmly against your cheek. Keep both eyes open, (this reduces eye strain,) and hold the gem in front of the loop. Next, position the gem in front of the loupe. Move it slowly towards and away from the loop until it comes into focus. Then practice adjusting the focus from the top surface to the far side. On a small gem you can get the entire stone in focus at once. On a larger gem you will have to focus on one area at a time.