"Precious stones" is a term that is usually used in reference to four types of gems: diamonds, rubies, sapphires, and emeralds. Some people have included opal, jade or pearls in the "precious stones" class, but these have not received persistent and widespread use. Separating stones into "precious" and "semiprecious" classes has led many people to believe that "precious stones" are more important and more valuable than "semiprecious stones." This idea has somewhat been supported by the fact that diamonds, rubies, sapphires and emeralds account for over 98% of the dollar value of U.S. gemstone imports for consumption reported by the United States Geological Survey.

The terms "semiprecious stones" and "semi-precious stones" are used for all varieties of gemstones that are not categorized as "precious." Any gemstone suitable for being used in personal adornment would be included. Semiprecious stones include gemstones fashioned from: agate, amber, amethyst, aquamarine, aventurine, chalcedony, chrysocolla, chrysoprase, citrine, garnet, hematite, jade, jasper, jet, kunzite, lapis lazuli, malachite, moonstone, obsidian, onyx, peridot, rhodonite, sunstone, tiger's eye, tanzanite, topaz, turquoise, tourmaline and many other materials.

The first century Jewish historian Josephus believed there was a connection between the twelve stones in Aaron's breastplate (signifying the tribes of Israel, as described in the Book of Exodus), the twelve months of the year, and the twelve signs of the zodiac. Translations and interpretations of the passage in Exodus regarding the breastplate have varied widely, with Josephus himself giving two different lists for the twelve stones.