The only gemstones made by living creatures, rare NATURAL PEARLS are produced by mollusks who layer calcium carbonate around a microscopic irritant. Most pearls used commercially today are FRESHWATER PEARLS, cultured or farmed by implanting a grafted piece of shell into freshwater pearl mussels. SHELL PEARLS, also known as simulated or replica pearls are made from mother-of-pearl. Pearl is the birthstone for June.
The thick inner shell of the marine gastropod abalone is composed of nacre, or mother-of-pearl. In many species this layer is highly iridescent, making it especially desirable for use in jewelry.
One of the most abundant minerals in the Earth's crust, quartz displays the greatest profusion of colors, patterns, and textures of any mineral. Gems cut from individual quartz crystals include amethyst, smoky quartz, rock crystal, citrine, and rose quartz. Finely grained quartz, which ranges from translucent to opaque, is typically carved or cut as cabochons or beads.