The Hand Loupe is the least expensive piece of equipment (as little as $15. u.s.) and fits easily into a pocket, purse or briefcase. Once you learn to use it, you will begin to see why it is called: "the Gemologist's Best Friend."
magnification is the most useful. Higher than that, and the depth of
field, (the area that remains in focus), is so small that the Loupe
becomes difficult to use...
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 always easy to achieve with a little thought. The only limitation is having too little light to see well.
hold your loupe hand firmly against your cheek. Keep both eyes open,
(this reduces eye strain,) and hold the gem in front of the loupe. Move
it slowly toward and away from the loupe until the gem 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. Larger
gems require that you focus on one area at a time.