If it is correct, it should be emeralds, also called metamorphic rocks, but some sapphires and garnets also have color-changing effects, and some artificial gem will also change color. If your identification is a natural gem, it should be an emerald from your description. If this kind of gem is relatively large, with less impurities and beautiful color change (obvious discoloration and beautiful color), then its price is higher than that of ruby, sapphire and emerald, and this kind of gem is rare and difficult to meet. So I advise you, if it is identified as a natural gem with good color, use it as a family heirloom and don't sell it easily.