Semi-precious gemstones are minerals or organic compounds used in jewelry and adornment. They differ from the four cardinal gems, diamond, sapphire, ruby and emerald, because they are more plentiful and therefore, are usually less expensive. Amethyst was once considered the fifth cardinal gem, but recent discoveries of extensive South American deposits have led to its re-classification as a semi-precious gem. A large proportion of the semi-precious stones are of the silicate class of mineral, which composes 90% of the earth’s crust.
One way to economize with jewelry is to replace cardinal gems with semi-precious stones of a similar color. Zircon, which shouldn’t be confused with cubic zirconium, is a normally colorless stone that makes for an excellent diamond substitute. In fact people wishing to avoid counterfeit diamonds might consider using zircon as a gem replacement.
Many royal families have been surprised to discover that the emerald treasures they owned were actually peridot, the crystal form of olivine. Though more yellow-green in color, peridot is easily confused with the more expensive emerald, and a lovely gem in its own right. Another emerald alternative is the creamy-green jade, known in China as the royal gem. Extremely variable in color, jade can be anywhere from pale apple-green with milky stripes to the dark even luster of imperial jade.
For those who prefers sapphires, numerous semi-precious stones exist as substitutions. Turquoise, frequently seen in Native American jewelry, is a sky blue stone that can alter shades with skin exposure. It has a waxy luster and occasionally white streaks. Aquamarine, a semi-precious stone from the same family as emeralds, is a near-translucent stone with a blue tinge. Topaz is often heat-treated to create a deep blue that is most reminiscent of a sapphire.
If the drama of a ruby is appealing, consider the blood-red garnet. The garnet ranges from a true red to a dark maroon, and carries far more sparkle than the ruby. It is even said that Noah used a garnet lantern to aid him in steering the ark.
Semi-precious stone varieties do not end with their similarities to the cardinal gems. Moonstones, a fabled gem from Sri Lanka, can appear almost colorless, but seem to carry a mysterious grey shimmer called “adularescence” that many once believed changed according to the moon cycles. Opals, from deep Australian and New Zealand mines, appear to be a pearl-grey or blue, but tiny silicate micro crystals refract light through the gem in rainbows.
Other semi-precious stones are not stones at all, rather organic compounds such as amber. This hardened sap of ancient trees takes on a lovely golden brown hue and often contains small fossils. Coral, a pinkish-red gem, is cleaned and polished material from the coral rubrum and corallium japonicum species of coral tree. Also from the sea is the pearl, a highly prized stone harvested from oysters and noted for its sheen.
Semi-precious stones range in price based on size, quality and authenticity. Many semi-precious stones are lab treated to enhance color and remove flaws, and these are correspondingly less expensive. For loose semi-precious stones, prices can range from a few US Dollars (USD) to several hundred depending on the size and quality.