Gemstones are classified into two categories, Precious and Semi-Precious, on the basis of their characteristics.
Precious Stones
Gemstones which are highly valuable for their hardness and rarity, are known as Precious Stones. Precious Stones are generally expensive in comparison of Semi-Precious Stones.Precious stones include Diamonds, Emeralds, Rubies, and Sapphires.
Semi-Precious Stones
Gemstones those are valued for their beauty and not covered under any one of the four ‘Precious Stones’, are known as Semi-Precious Stones. Semi-Precious Stones are available in all price ranges from low priced to high priced. Semi-Precious stones are Alexandrite, Amethyst, Aquamarine, Citrine, Garnet, Iolite, Onyx, Opal, Pearl, Peridot, Tanzanite, Topaz, Tourmaline etc.