Gemstones fall into 2 categories:
Precious gemstones – Diamond, Ruby, Emerald and Sapphire. These gemstones are in much higher demand and carry a higher value.
Semi-Precious gemstones – These include all the other colored stones. Some of the most popular are Tanzanite, Garnet, Amethyst, Opal, Topaz, and Tourmaline.
Birthstones are comprised of both Precious and Semi-Precious gemstones: