Stars and Gemstones - Precious Stones
A natural gemstone is a mineral, stone, or organic matter that can be cut and polished or otherwise treated for use as jewellery or other ornament. A precious gemstone has beauty, durability, and rarity, whereas a semiprecious gemstone has only one or two of these qualities.
A gem is a gemstone that has been cut and polished.
Diamond, corundum (ruby and sapphire), beryl (emerald and aquamarine), topaz, and opal are generally classed as precious stones. All other gemstones are usually classed as semiprecious.