Step 3: Practical Gemology
Adapting a Balance Scale
You can adapt almost any balance-type scale for specific gravity testing. All you need to do is find a way to submerge one pan in water. If you look in your cupboard, you’ll certainly find something suitable. Take an appropriate sized cup or jar and place it so the weighing pan will rest comfortably inside. It must ride freely without touching any of the sides.
First, weigh the gem as usual in air. Then, fill the cup or jar with enough water to completely submerge the gem. Make sure there are no air bubbles on the surface of your gem. Place your gem on the pan that is underwater and weigh it again.
Adapting an Electronic Scale
If you have an electronic scale, you can make a simple balance beam to go along with it to measure specific gravity. The key factor to consider when making a balance beam is to get it as sensitive as possible. The length of the beam and the point of the fulcrum determine the scale’s sensitivity. A longer beam will be more sensitive to changes in weight. A fulcrum with a…