GEMSTONES jewelry stones are classified into precious and semi-precious. The precious ones are diamond, sapphire, ruby and emerald. There are other expensive but very rare ones, such as Sri Lankan serendibita, grandidierita and taaffeiete. The semi-precious ones are lapiz lazuli, rose quartz, amethyst, onyx, aquamarine, topaz, citrine, malachite, turquoise, agate, spinel, moonstone, garnet, opal, alexandrite, tanzanite and others. Some consider rose quartz, agate, onyx or onyx, malachite and pencil lazuli to be precious for commercial and non-scientific reasons.
