How To Examine Gemstones With The Loupe And Tweezer

Upon first glance, the examination of a stone with the loupe and tweezer seems simple. However, the proper technique not only will help in locating inclusions, but it will show that the user has experience in handling and examining gemstones.

Below are a few tips for using the loupe and tweezer:

Loupe
Clean the stone carefully with a piece of cotton cloth and then pick it up directly with tweezers. Touching the stone with fingers may leave grease marks which might resemble inclusions.

If the right eye is to be used, hold the loupe in the right hand. Hold it as close as possible to the eye (or glasses), for the closer it is to the eye, the larger the field of view.

The stone to be examined should be held with tweezers and both hands should be in contact with each other. This eliminates shaking and unsteadiness.

Lighting is the next consideration and is of vital importance. One commonly used but ineffective method is to place the light directly behind the stone. The result is that rear facets reflect the light away from the stone. This leaves the stone's interior dark and the eyes blinded by glare. A much better technique makes use of a table lamp positioned so that the light faces straight down. The stone is held just next to the edge of the lamp shade so that light enters the stone from the side. Now the glare is eliminated and inclusions are much more readily seen.

Tweezer
A good pair of tweezers is another essential piece of equipment. These should be specifically designed for gemstone use. To avoid corrosion, tweezers should be made of stainless steel. Critical is the knurling found on the inside of the tips, to keep the gem from slipping. Better examples actually include a groove designed to grip the gem's girdle.

In terms of color, black is best, because it eliminates reflections. Brushed (not polished) steel is also okay; avoid brass-colored tweezers, which make rubies appear redder. In terms of tip size, the narrow tips work best with melee, but are difficult to use on large stones. For stones of 1 ct or more, a wider tip is preferred.