Gemmy denotes the ability to cut gem stones from the material. A gem stone can be either a cabochon or a faceted stone. The more transparent and flaw free the material the more likely it will be cut into a faceted stone. After the stone is cut its color and freedom from flaws will determine its value. Eye clean under 10X magnification are the most desirable and the most valuable. Usually you can go on line and compare the quality of your stone with those being offered to get an idea of its value.