Understanding Gems; there are many types of gems, precious and semi-precious. There are stones that are not real, some are glass some are synthetic, and other materials. Ther minerals, emeralds, diamonds, sapphires, rubys, and others like garnets, tanzanite sapphires that are dazzeling and can be very very valuable. Often times manipulations are only detecable by professional jewelers. Most all stones are touched by in some way by man to enhance their looks. So when looking at stones know that almost all stones touched by man. They all look beautiful.