December 9, 2019

If your birthday is in December, you have the choice of three bluish birthstones—the gems associated with the month of your birth—turquoise, zircon, and tanzanite. Turquoise is a mineral widely used as a gemstone. It is prized for its color, which ranges from sky-blue to blue-green or yellow-green. The mineral zircon comes in many colors, but the blue variety is most popularly worn in jewelry. Tanzanite, a semiprecious gemstone, is a type of a mineral called zoisite. Trichroic (three-colored) tanzanite crystals are often deep blue or purple.

Turquoise is a bright blue or blue-green mineral widely used as a gemstone. Credit: © Akulinina Olga, Shutterstock

Turquoise is relatively soft, and so it is easy to shape and polish. It has a dull, waxy luster and is nearly opaque (nontransparent). Turquoise consists chiefly of a hydrous aluminum phosphate, a compound in which aluminum and phosphorus are chemically combined with water. It also contains copper, which gives it its bluish color. Turquoise occurs in the arid regions of Iran, Tibet, Mexico, and the southwestern United States. The mineral’s pastel blue color made it popular with royalty and others of importance from these areas, particularly in the ancient Chinese, Egyptian, Persian, and the Aztec and other Native American civilizations. Turquoise was once thought to promote good health, wealth, and protection from evil spirits.

Zircon is a birthstone of December. Credit: © Shutterstock

Zircon originates in the ancient layers of the Earth’s crust. It is composed chiefly of the elements silicon, oxygen, and zirconium. Zircon also contains smaller amounts of such elements as hafnium, iron, and the lanthanides. Some zircons also contain the radioactive elements thorium and uranium. Zircon crystals may be reddish-brown, yellow, green, blue, or colorless. The colorless variety of zircon can sometimes resemble a diamond, but it is not to be confused with the unrelated synthetic diamond substitute, cubic zirconia. Zircon is used in the ceramics industry and in making parts for nuclear reactors. Blue zircon crystals have long been used for jewelry. In ancient times, the mineral was thought to have calming properties that aided sleep, decision-making, self-confidence, and general wisdom. Zircon is found in many parts of the world, but Australia produces more of the mineral than any other country.

Tanzanite is a relative newcomer to both the birthstone list and the world at large. The mineral was discovered in 1967 in Tanzania, for which it was named, and added as a December birthstone in 2002. Tanzania is the only known source of tanzanite. Because the supply is limited, it is quite expensive. Tanzanite is cut into gemstones with numerous facets (flat, polished surfaces), which emphasize its light-reflecting quality. The gemstones are used in such jewelry as rings, earrings, and pendants.

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Birthstones, according to tradition, bring good luck when worn by a person born in the associated month. Credit: WORLD BOOK illustrations by Paul D. Turnbaugh

According to tradition, a birthstone brings good luck to a person born in its month. Each birthstone also corresponds to a sign of the zodiac. The belief in birthstones may have come from a Bible story about Aaron, the first high priest of the Israelites. The story describes Aaron’s breastplate, which was decorated with 12 precious stones. Early writers linked these stones with the 12 months of the year and the 12 signs of the zodiac. The custom of wearing a stone that represented a person’s zodiac sign probably originated in Germany or Poland in the 1700′s.

November 11, 2019

If your birthday is in November, your birthstone—the gem associated with the month of your birth—is the topaz. Topaz is a compound of aluminum, fluorine, silicon, oxygen, and hydrogen. The mineral is commonly white or light colored, but trace impurities can give topaz crystals a wide variety of colors. Topaz is often cut into gems, and its myriad colors give it a lovely versatility in jewelry.

Topaz is the birthstone for the month of November. Credit: © Albert Russ, Shutterstock

The ancient Greeks believed topaz increased physical strength. In the Middle Ages, topaz was worn to ward off danger, break magic spells, or maintain good health. Topaz was also thought to improve eyesight and at times make a person invisible. People thought that beneath a pillow, topaz prevented nightmares, and in a home the gem protected from fires. Gold-colored topaz was thought to attract wealth as well as the favors of royalty or high government. In India, topaz was believed to encourage long life, beauty, and intelligence. “Imperial” topaz was a favorite gem of the Russian  czars.

Small amounts of topaz occur in both igneous rocks (rocks formed when molten rock cools and solidifies) and metamorphic rocks (rocks formed by heat and pressure). Jewelers cut transparent topaz crystals into gems. The most desirable topaz gems range in color from completely colorless to gold, orange, blue, and pink. Exposing some topaz crystals to heat or radiation can dramatically enhance or even change their color.

Jewelers sell blue topaz as a substitute for the gem aquamarine (a birthstone of March). Citrine, a yellow or brownish variety of quartz, is sometimes sold as a substitute for topaz. Topaz is found in many parts of the world. Brazil produces most of the world’s gem-quality topaz. Many museum collections have large, beautiful topaz crystals that weigh hundreds of pounds or kilograms. The gem gallery at the National Museum of Natural History at the Smithsonian Institution in Washington, D.C., is home to the 48.86-carat Whitney Flame Topaz. It is one of the finest imperial topaz gemstones in the world, notable for its large size and fiery red color.

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Birthstones, according to tradition, bring good luck when worn by a person born in the associated month. Credit: WORLD BOOK illustrations by Paul D. Turnbaugh

According to tradition, a birthstone brings good luck to a person born in its month. Each birthstone also corresponds to a sign of the zodiac. The belief in birthstones may have come from a Bible story about Aaron, the first high priest of the Israelites. The story describes Aaron’s breastplate, which was decorated with 12 precious stones. Early writers linked these stones with the 12 months of the year and the 12 signs of the zodiac. The custom of wearing a stone that represented a person’s zodiac sign probably originated in Germany or Poland in the 1700′s.

October 21, 2019

If your birthday is in October, your birthstones—the gems associated with the month of your birth—are the opal and the tourmaline. Opal is a glassy material, some of which is valued as a gem for its flashes of color. It consists of water and a mineral called silica, the most common ingredient in sand. The tourmaline is any of a group of boron-containing minerals often found in granite. Tourmalines are used as gemstones and for industrial purposes.

The glassy opal is one of the birthstones of October. Credit: © Bjoern Wylezich, Shutterstock

Traditionally, opals have been worn by royalty and others of importance, and the gems were prized for their brilliant colors and translucent qualities. Many people thought opals were beneficial to the eye, and they were worn to cure eye diseases. Some people believed opals attracted money, and that they could make a person invisible. Thus they were popular with thieves. Black opals were thought to aid magicians or practicers of supernatural “black arts.”

Much opal is white, gray, brown, or black. Some opal shows a brilliant flash of color, called play of color, on top of its background color. Opal with play of color is called precious opal. Opal without color play has little or no gem value, unless it is clear or brightly colored. Opal without gem value is called common opal or potch. Australia is the main modern source of opals, but they can be found in many parts of the world. One of the largest opals ever found, the Andamooka Desert Flame, weighed over 15 pounds (6.8 kilograms) when found in Australia in 1969.

The tourmaline crystal shows a rainbow of colors. Credit: © Albert Russ, Shutterstock

The tourmaline, sometimes called the rainbow of gemstones, has traditionally been worn as a jewel of love, protection, and harmony. The gems were also thought to help people connect with their inner selves, and thus the tourmaline aided with self-realization and understanding.

Tourmalines vary greatly in color. The most common tourmalines include elbaite, dravite, and schorl. Elbaite, which is rich in lithium, can appear pink, blue, green, or yellow. Dravite, a magnesium-rich tourmaline, usually appears brownish. Schorl, rich in iron and manganese, is usually black. The color of some tourmaline crystals varies from the center to the edges. Watermelon tourmaline, for example, appears pink in the center and green at the edges. These changes indicate a change in conditions as the crystal formed.

Tourmaline is piezoelectric—that is, its crystals can develop an electric charge when stretched or squeezed. Tourmaline has been used in radio transmitters and pressure sensors. Scientists use slices of tourmaline in the study of polarized light (light that vibrates in a single direction). Jewelers commonly cut transparent and flawless tourmaline crystals into gems.  Main sources for tourmalines include Brazil, India, Sri Lanka, and several countries in Africa.

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Birthstones, according to tradition, bring good luck when worn by a person born in the associated month. Credit: WORLD BOOK illustrations by Paul D. Turnbaugh

According to tradition, a birthstone brings good luck to a person born in its month. Each birthstone also corresponds to a sign of the zodiac. The belief in birthstones may have come from a Bible story about Aaron, the first high priest of the Israelites. The story describes Aaron’s breastplate, which was decorated with 12 precious stones. Early writers linked these stones with the 12 months of the year and the 12 signs of the zodiac. The custom of wearing a stone that represented a person’s zodiac sign probably originated in Germany or Poland in the 1700′s.

September 11, 2019

If your birthday is in September, your birthstone—the gem associated with the month of your birth—is the sapphire. The sapphire, a variety of the mineral corundum, is a hard and clear gem. The best known sapphires are blue. Their color results from small amounts of iron and titanium in the stone. Sapphires are also found in many other colors, including yellow, green, white, black, violet, and orange. The red variety of corundum is known as a ruby, the birthstone of July. Sapphires have long been used in jewelry and decorative objects.

Sapphires are shown cut and polished, left, and uncut, right. The sapphire is the birthstone of the month of September. Credit: © Biophoto Associates/Photo Researchers

Traditionally, sapphires symbolize faithfulness, nobility, purity, and sincerity. Sapphires were once thought to allow clarity of mind and to ward off evil spirits. As the stone of the planet Saturn, sapphires offered a magical portal to heavenly realms. In ancient Greece and Rome, sapphires protected people from envy and harm. The gems have long been popular with royalty, and Roman Catholic bishops and other clergy have worn sapphire rings for centuries. The sapphire’s rich blue color is used to describe blue objects of particular beauty, such as Sapphire Lake in northern California. The sapphire is the traditional gem gift for a 45th wedding anniversary. In 2017, Queen Elizabeth II became the first British monarch to mark a 65th year on the throne with a sapphire jubilee.

The most valuable sapphires once came from Indian Kashmir. They are a magnificent cornflower blue, the color to which all sapphires are compared. Today, Thailand is the most important source of blue sapphires. Blue and fancy sapphires are also found in the Sapphire Mountains (naturally) of Montana and in Australia, Myanmar, and Sri Lanka.

Lovely star sapphires contain needles of the mineral rutile that reflect light in six starlike rays. The most highly prized star sapphires are blue. Black or white star sapphires are less valuable. One of the largest blue star sapphires, the Star of India, weighs 563 carats, or about 4 ounces (110 grams). It is on exhibit in the American Museum of Natural History in New York City.

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Birthstones, according to tradition, bring good luck when worn by a person born in the associated month. Credit: WORLD BOOK illustrations by Paul D. Turnbaugh

According to tradition, a birthstone brings good luck to a person born in its month. Each birthstone also corresponds to a sign of the zodiac. The belief in birthstones may have come from a Bible story about Aaron, the first high priest of the Israelites. The story describes Aaron’s breastplate, which was decorated with 12 precious stones. Early writers linked these stones with the 12 months of the year and the 12 signs of the zodiac. The custom of wearing a stone that represented a person’s zodiac sign probably originated in Germany or Poland in the 1700′s.

August 19, 2019

If your birthday is in August, you have two birthstones—the gems associated with the month of your birth: peridot and sardonyx. Peridots are a variety of a common rock-forming mineral called olivine. A high iron content gives peridots their distinctive green color. The sardonyx is a multi-colored variety of chalcedony, a fine-grained form of the mineral quartz. Most sardonyx has straight or slightly curved bands of reddish-brown and white. Both peridot and sardonyx have long been used in jewelry and decorative objects.

Peridot is one of two August birthstones. The other is sardonyx. Credit: © Albert Russ, Shutterstock

Peridots have been known since Biblical times, and legend says the stones improve health, guard against insanity, and slow the human aging process. Peridots are also said to increase assertiveness, patience, and clarity of thought and to encourage prosperity and happiness. Jewelers cut and polish the highest-quality peridot stones so that each gem has many flat surfaces called facets. Faceted peridots are used in all types of fine jewelry. Jewelers cut lesser-quality peridots into a rounded style called cabochon or polish them with abrasives in a process called tumbling. These lesser-quality peridots are used in costume jewelry and decorative objects. The earliest source of peridots was Jazirat Zabarjad (St. John’s Island), off the Egyptian coast in the Red Sea. In the United States, Arizona and New Mexico are important commercial sources of peridots.

Sardonyx is a multi-colored variety of chalcedony. Credit: © Vlad3563/Dreamstime

In ancient Egypt, sardonyx was considered a protective stone, and it was used to ward off evil. Modern folklore credits sardonyx with encouraging confidence, creativity, happiness, integrity, optimism, and even virtuous behavior. It is said to help students preparing for exams, authors dealing with writers block, or anyone faced with a job requiring mental discipline. Jewelers usually cut sardonyx flat or with a domed shape to bring out the bands of color. Cameos (engraved gems) are sometimes cut from sardonyx to take advantage of its color. The chief sources of sardonyx are Brazil, India, and Uruguay.

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Birthstones, according to tradition, bring good luck when worn by a person born in the associated month. Credit: WORLD BOOK illustrations by Paul D. Turnbaugh

According to tradition, a birthstone brings good luck to a person born in its month. Each birthstone also corresponds to a sign of the zodiac. The belief in birthstones may have come from a Bible story about Aaron, the first high priest of the Israelites. The story describes Aaron’s breastplate, which was decorated with 12 precious stones. Early writers linked these stones with the 12 months of the year and the 12 signs of the zodiac. The custom of wearing a stone that represented a person’s zodiac sign probably originated in Germany or Poland in the 1700′s.

July 5, 2019

If your birthday is in July, your birthstone—the gem associated with the month of your birth—is the beautiful and valuable ruby. A red gem variety of the mineral corundum, rubies are called sapphires if they are any color other than red. Since ancient times, rubies have been treasured for their beauty as well as their symbolic value in folklore, religion, and superstition.

The ruby, the birthstone for July, is often used to make jewelry such as rings. This ring is set with a ruby and diamonds. Credit: © JupiterMedia/Alamy Images

Early cultures valued rubies for their resemblance in color to human blood, and the gems were thought to hold the power of life. Rubies were later associated with beauty, love, passion, wealth, and wisdom. Ancient Sanskrit texts refer to the ruby as “the king of precious stones,” and Hindu legend says that those who offered rubies to the god Krishna were granted rebirth as emperors. Rubies were thought to protect those who wore them, even bestowing invincibility in battle. It was not enough to simply wear rubies, however—they were often inserted in the skin. Rubies were also sometimes included in the foundations of buildings to ensure good fortune. Rubies have long adorned earrings, necklaces, rings, and other jewelry, and they are the traditional gift for a 40th wedding anniversary.

Chemically, a ruby is an aluminum oxide. Rubies get their color from traces of chromium. The red of most rubies has a brownish or yellowish tint. The rarest, most highly prized rubies are pure “pigeon-blood red.” Rubies and sapphires are second only to diamonds in hardness, and fine-quality rubies are among the costliest of all gems. The finest rubies come from Myanmar. Other primary producers of rubies are Cambodia, Kenya, Madagascar, Tanzania, Thailand, and Zimbabwe.

A star ruby cabochon shows a six-rayed star within it when seen in a bright light. A cabochon is a rounded, polished stone. The largest known natural ruby, named the “Eminent Star,” weighs 6,465 carats, or almost three pounds (1.36 kilograms). Millions of carats of inexpensive synthetic rubies are made each year. But a demand for real gems has allowed the natural stones to maintain their high value. It can be hard to distinguish between natural and synthetic rubies, even for experts. Experts are also challenged when determining whether the color of a natural ruby has been improved by heating.

June 10, 2019

If your birthday is in June, you can choose between three birthstones—the gems associated with the month of your birth: alexandrite, moonstone, or pearl. Alexandrite is a rare gem variety of the mineral chrysoberyl. The most highly valued alexandrite appears green like an emerald (May’s birthstone) in natural light, but looks red like a ruby (July’s birthstone) in artificial light. Moonstone is a whitish variety of the mineral feldspar. Light will shine through moonstone, but not so clearly as through glass. The pearl is one of the most valuable gems. Large, perfectly shaped pearls rank in value with the most precious stones.

Alexandrite appears green in natural light. Credit: © Shutterstock

Alexandrite was first discovered in the Ural Mountains of Russia in 1833. The stone was named after Alexander II, who later became the czar of Russia. Today, alexandrite is still mined in Russia. Other countries that produce alexandrite include Brazil, Myanmar, Sri Lanka, Zambia, and Zimbabwe.

Moonstone reflects light with a bluish or pearly-colored sheen that comes from inside the stone. Credit: © J. Palys, Shutterstock

Moonstones have a metallic or iridescent luster. This optical phenomenon, called adularescence or schiller, results from light reflecting off thin layers of feldspar. The name moonstone came from ancient legends that said the gems were created by beams of light from the moon. During a full moon, the gem was thought to have strong powers that attracted good fortune or love. Today, moonstones—many of which come from Sri Lanka—commonly decorate earrings and necklaces.

This photograph shows a pearl with a rosy hue inside an open oyster. Credit: © FoodPhotography/Getty Images

Pearls are different from other gems. Most gems are minerals that are mined from beneath the earth. But pearls are formed inside the shells of oysters. Oysters and other shell-forming mollusks make a special substance, called nacre or mother-of-pearl, that lines the insides of their shells. This smooth lining is called the nacreous layer, or pearly layer, and it is often lustrous. It is formed by a fleshy body organ called the mantle. When a foreign substance, such as a bit of shell or a tiny parasite, enters the body of the mollusk, the mantle begins to work. It covers the invading substance with thin sheets of nacre. It builds successive circular layers of nacre until the foreign body is enclosed in the shell-like substance, forming the pearl.

Pearls were treasured among many ancient cultures. The often white color of the “queen of gems” has long symbolized purity, but pearls can also be “black” (dark gray), cream, gold, orange, or pink. Round pearls, suitable for necklaces, are the most valuable. Next in value are the button-shaped and drop-shaped pearls. These are often used for earrings.

Until the 1940′s, the chief pearl-oyster beds were found in the Persian Gulf, near the island country of Bahrain. Other natural pearl-oyster beds were located in the South Pacific Ocean. Thousands of oysters had to be collected to produce even a small handful of pearls. For this reason, natural pearls were extraordinarily expensive. Today, few natural pearls are harvested for jewelry because the farming of cultured pearls produces pearls more cheaply. Cultured pearls are created by oysters planted in carefully selected oyster beds. People then “encourage” pearls to form (usually within about three years) by placing tiny pellets made of nacre or mussel shell inside the oyster shells.

According to tradition, a birthstone brings good luck to a person born in its month. Each birthstone also corresponds to a sign of the zodiac. The belief in birthstones may have come from a Bible story about Aaron, the first high priest of the Israelites. The story describes Aaron’s breastplate, which was decorated with 12 precious stones. Early writers linked these stones with the 12 months of the year and the 12 signs of the zodiac. The custom of wearing a stone that represented a person’s zodiac sign probably originated in Germany or Poland in the 1700′s.

May 17, 2019

If your birthday is in May, your birthstone—the gem associated with the month of your birth—is the emerald. The emerald is a rich green gemstone that is a variety of the mineral beryl. It owes its color to minute amounts of chromium in the crystals. The value of an emerald depends on its color and its freedom from flaws and inclusions (other substances enclosed in the crystals). An emerald with a blue tint is more valuable than one with a yellow tint. Most emerald crystals contain minute fractures, which are sometimes called veils, and various kinds of inclusions. Perfect emeralds are very rare and therefore may be more expensive than diamonds (April’s birthstone).

The emerald, such as this one with a blue tint, is the birthstone for the month of May. Credit: © Carl Frank, Photo Researchers

Emeralds have been used in jewelry and other adornments since the days of ancient Egypt. “Cleopatra’s Mines,” an ancient system of emerald mines, can still be visited in the Wadi El Gamal National Park near the Red Sea coast, east of Aswān. The people of ancient Greece, India, Persia, and Rome also treasured emeralds. The ancient Aztec and Inca civilizations of the Americas did too, mining emeralds in the mountains of modern day Colombia. Today, Colombia continues to produce the world’s finest emeralds. Afghanistan, Brazil, India, Madagascar, Pakistan, Russia, Zambia, and Zimbabwe also produce emeralds.

The emerald is a traditional birthstone for Cancer (June 21-July 22), a sign of the zodiac. It is also a traditional gem gift for the 20th, 35th, and 55th wedding anniversaries. In the past, some people believed emeralds possessed magical powers. According to legend, an emerald in the mouth guarded against dysentery, aided eyesight, and allowed a person to see the future. Emeralds were also believed to reveal the truth (particularly regarding a lover’s fidelity), protect against evil spells, and cure such diseases as cholera and malaria. The bright green color of the emerald is also used to describe such verdant (lush green) places as Ireland (the Emerald Isle) and Seattle (the Emerald City—also an important place in The Wizard of Oz). Thailand’s most sacred religious icon is the Emerald Buddha, an ancient figurine carved from green jade rather than emerald.

According to tradition, a birthstone brings good luck to a person born in its month. Each birthstone also corresponds to a sign of the zodiac. The belief in birthstones may have come from a Bible story about Aaron, the first high priest of the Israelites. The story describes Aaron’s breastplate, which was decorated with 12 precious stones. Early writers linked these stones with the 12 months of the year and the 12 signs of the zodiac. The custom of wearing a stone that represented a person’s zodiac sign probably originated in Germany or Poland in the 1700′s.

April 24, 2019

If your birthday is in April, your birthstone—the gem associated with the month of your birth—is the diamond. The diamond is the hardest naturally occurring mineral, and also one of the most valuable natural substances. Because of its hardness, the diamond is the most lasting of all gemstones. In Europe, Japan, and North America, diamonds are widely used in engagement and wedding rings. Diamonds are also used in industry for cutting, grinding, and boring other hard materials. About half of the world’s natural diamonds are suitable only for industrial use. A small percentage are set in jewelry.

This photograph shows a naturally occurring diamond embedded in a sample of the rock kimberlite. Diamonds may be mined from pipe-shaped deposits of kimberlite, which fill the throats of extinct volcanoes. Natural diamonds are dull and must be cut by skilled jewelers to bring out the gem’s distinctive sparkle. Credit: © Matteo Chinellato, ChinellatoPhoto/Exactostock/SuperStock

Diamonds have been treasured at least since the days of the ancient Roman naturalist Pliny the Elder. He wrote: “Diamond is the most valuable, not only of precious stones, but of all things in the world.” Trade in diamonds was also prevalent in ancient India, and by the Middle Ages diamonds were fashionable accessories in several parts of the world. The diamond is a traditional birthstone for Aries (March 21-April 19), a sign of the zodiac. It is also a traditional gem gift for a 60th wedding anniversary—an event also called a diamond anniversary. In the past, some people believed diamonds possessed magical powers. According to legend, wearing a diamond could relieve fatigue or cure mental illness.

Diamonds are crystals that are made up almost entirely of carbon. Some diamond crystals have six faces, but most form octahedrons,which have eight faces. Natural diamonds probably form in Earth’s upper mantle—the zone beneath the crust—where high temperature and pressure cause carbon to crystallize. Diamonds are later brought to Earth’s surface by volcanic activity. The gems can be found in several places around the world, but the leading producers of natural diamonds include Australia, Botswana, Canada, the Democratic Republic of the Congo, and Russia.

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Birthstones, according to tradition, bring good luck when worn by a person born in the associated month. Credit: WORLD BOOK illustrations by Paul D. Turnbaugh

According to tradition, a birthstone brings good luck to a person born in its month. Each birthstone also corresponds to a sign of the zodiac. The belief in birthstones may have come from a Bible story about Aaron, the first high priest of the Israelites. The story describes Aaron’s breastplate, which was decorated with 12 precious stones. Early writers linked these stones with the 12 months of the year and the 12 signs of the zodiac. The custom of wearing a stone that represented a person’s zodiac sign probably originated in Germany or Poland in the 1700′s.

March 11, 2019

If your birthday is in March, you have two birthstones (gems associated with the month of your birth): aquamarine and bloodstone (a variety of chalcedony). Aquamarine is a light blue or bluish-green gem. It is cut in facets (polished flat surfaces) and used in all types of jewelry. Bloodstone is a dark green gem with red spots. It too is used in jewelry, but it is also associated with Christianity.

Aquamarine is one of two birthstones for the month of March. Credit: © Albert Russ, Shutterstock

Aquamarine is a variety of the mineral beryl. The most popular color is a clear sky-blue. Aquamarine is often treated with heat to improve its color. Almost all aquamarine is transparent. Aquamarines have been known since ancient times, when legends said the gems could help people relax or could act as an antidote to poison. The ancient Romans believed the gem could cure laziness and produce courage. The most important source of aquamarines is Brazil.

Bloodstone is another birthstone of March.
Credit: © Shutterstock

Bloodstone, a variety of the mineral Chalcedony, is related to agate, carnelian, and onyx. Chalcedony was named for the ancient town of Chalcedon, in what is now Turkey, which is near deposits of the mineral. Bloodstone is sometimes called Martyr’s Stone or Christ’s Stone because legend attributed the gem’s red spots to the blood of Jesus Christ. The ancient Greeks called bloodstone heliotrope (also a type of flower) for the way it reflects light. The Babylonians used bloodstone to make amulets, decorative vessels, and seals.

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Birthstones, according to tradition, bring good luck when worn by a person born in the associated month. Credit: WORLD BOOK illustrations by Paul D. Turnbaugh

According to tradition, a birthstone brings good luck to a person born in its month. Each birthstone also corresponds to a sign of the zodiac. The belief in birthstones may have come from a Bible story about Aaron, the first high priest of the Israelites. The story describes Aaron’s breastplate, which was decorated with 12 precious stones. Early writers linked these stones with the 12 months of the year and the 12 signs of the zodiac. The custom of wearing a stone that represented a person’s zodiac sign probably originated in Germany or Poland in the 1700′s.