History of garnet
There are many different myths about the origins of garnet. One such myth suggests that the garnet originated with Persephone, the Greek goddess of sunshine. Persephone was captured by Hades, the god of the underworld. Before Hades released Persephone, he wanted to guarantee her return, so he gave her some pomegranate seeds. The word garnet comes from the Latin "granatus," which means seed. The next time you eat a pomegranate, you will notice the seeds' resemblance to garnet.
Science of garnet
Garnet is actually a group of six different stones: grossular (red to orange colors), almandine (red), pyrope (red and pink), spessartite (green-brown), andradite (brown to black), and uvarovite (emerald green). Garnets can be found in metamorphic rocks and sometimes in granites and volcanic rocks. These special minerals form deep underground, enduring extreme temperatures and pressures. For this reason, geologists may use garnets to study the temperature and pressure of the surrounding rock. Garnets belong to the isometric crystal class, which produces symmetrical, cube-based crystals.
*An alternate birthstone for January is clear rose-quartz. Quartz in a very hard, durable, and transparent mineral and is the most abundant semi-precious stone.
History of amethyst
According to Greek myth, Dionysius, god of intoxication, was angered by an insult from a mere mortal and swore revenge on the next mortal that crossed his path, creating fierce tigers to carry out his wish. Along came the unsuspecting Amethyst, a beautiful maiden on her way to pay tribute to the goddess Diana. Diana turned Amethyst into a statue of pure crystalline quartz to protect her from the tigers. Dionysus wept tears of wine in remorse at the sight of the beautiful statue. The god's tears stained the quartz purple, creating the gem we know today.
Science of amethyst
Amethyst is a member of the quartz family, occurring as crystals within rocks. Quartz often grow within cavities of cooling lava, forming geodes. Although the gem color must always be purple to be amethyst, it has a wide range of purple shades. Amethyst can occur as long prismatic crystals that have a six-sided pyramid at either end, or it can form as crystalline crusts called druzes that only show the pointed ends. Amethyst is popular for its color and crystal shapes that produce handsome, purple, sparkling clusters.
*An alternate birthstone for February is onyx, a variety of the cryptocrystalline quartz that is opaque or translucent and comes in different colors that are banded in straight and parallel lines.
Aquamarine's name comes from the words "aqua" and "mare," meaning water and sea, from its intense blue-green color. Because of its resemblance to the ocean, sailors used to wear talismans made of aquamarine depicting the god Neptune, who ruled the seas. With the help of their god, they believed the aquamarine would offer them protection from the elements.
Science of aquamarine
Aquamarine is a variety of the mineral beryl. Beryl generally forms inside granites as magma (molten rock) cools deep inside the Earth. Beryl comes in many different colors, ranging from clear to the deep green of the stones we know as emeralds. Aquamarine, though, is usually blue-green in color due to the presence of iron within the mineral's structure. Less desirable yellow or clear aquamarines can be heat-treated to produce the vibrant blue-green hue.
*An alternate birthstone for March is bloodstone, a dark green opaque (cryptocrystalline) quartz flecked with red spots.
History of diamond
Diamond is the most familiar gemstone and it has a rich and interesting history. Diamonds are known for their prismatic beauty and hardness, and they are highly valued for these and other qualities. At one time, it was even thought that if you took a diamond into bed with you, it would cure your illness!
Science of diamond
Diamond is a form of carbon with a tightly bound crystalline structure. It originates deep inside the Earth under intense pressure and high temperatures. Diamonds are brought up to the surface by very deep-seated volcanic activity. Diamond-bearing volcanoes are called kimberlies, and they erupted millions of years ago. Interestingly, both graphite (used in pencils) and diamond are forms of carbon, but they have very different structures and properties: graphite is opaque and soft, while diamond is transparent and the hardest mineral on Earth. These differences occur because diamond crystallizes in the isometric system while graphite crystallizes in the hexagonal system.
History of emerald
Thousands of years ago, the ancient Egyptians mined the Earth, suffering through extreme conditions to find the prized green emerald. Cleopatra was so taken with these stones that she claimed the mines for herself. In fact, she was known for wearing lots of huge emerald jewelry, and gave emeralds carved with her portrait to her important visitors.
Science of emerald
Emerald is another variety of beryl, the mineral that includes aquamarine (blue), heliodor (yellow to gold), and morganite (pink to peach). The reason for emerald's vivid green color is that chromium and iron infiltrated its mineral structure during formation. It is surprisingly common for emeralds to contain flaws and veins of chemicals called inclusions. These little imperfections are an accepted feature of the stone's identity.
*An alternate birthstone for May is chrysoprase, an bright apple-green variety of chalcedony (cryptocrystalline quartz), often called Australian Jade.
History of moonstone
Moonstone is a form of the mineral oligoclase feldspar. Moonstone's name comes from the fact that its shiny iridescent and refractive properties resemble the glowing moon. Moonstone (also called sunstone) can be blue-white or peach in color. Ancient peoples believed that the stone had mystical properties and could help with spiritual awareness. Some even believed that wearing this stone could cause invisibility for the wearer.
Science of moonstone
The strange light-refractive qualities of moonstone are caused by lamellar intergrowths inside the crystal. These structures form from layers caused by chemicals responding to hot and cold temperatures differently. When light enters the stone, it is bounced back and forth between these layers before it exits as the glowing moon-like effect we see.
History of ruby
The ruby is one of the most highly valued of all gems. Ancient Hindus referred to it as "the king of gems," and royalty used ruby to ward off evil because it was believed to have magical powers. One such magical power was that the ruby would get darker in the presence of evil and lighter when the evil was gone—but only if possessed by its rightful owner.
Science of ruby
Ruby originates from metamorphic rock, and is a variety of the mineral corundum, second only to the diamond in hardness. Rubies exist in a wide variety of colors, including blue, which is more commonly known as sapphire. Chromium is what causes the red color of rubies, however. Rubies can range in color from pale pinks to the deepest possible red, known as "pigeon blood." When rutile crystal inclusions are oriented in a specific pattern, a six-pointed star (called an asterism) becomes visible—these prized gems are called "Star Ruby."
*An alternate birthstone for July is carnelian, a translucent orange to reddish-brown version of the cryptocrystalline quartz.
History of peridot
The Arabic word "faridat," meaning gem, is where the name for the gem peridot comes from. Peridot's stunning beauty and bright color caused the ancient Egyptians to call it "the gem of the sun." It was believed that peridot glowed with its own inner light even after sunset, and that miners used to locate the stones at night to retrieve them during the day.
Science of peridot
Peridot is type of olivine, and comes in various shades of green, from light to a brilliant olive green. Olivine contains two types of minerals: fayalite and forsterite. Fayalite, with the mineral formula Fe2SiO4, contains large quantities of iron. Forsterite contains magnesium, and has a formula of Mg2SiO4. Olivine's formula is (Mg, Fe)2SiO4, showing the substitution of magnesium and iron. Peridot is the transparent form of forsterite.
*An alternative birthstone for August is the gem variety of jade. The green color in jade is from trace amounts of chromium in the mineral.
History of sapphire
Sapphires were believed to have special protective powers, such as preventing envy and protecting the wearer from poisoning. Some ancient cultures even thought that if a sapphire container held a venomous snake, it would die. In addition, people believed that sapphire had medical healing properties, such as the ability to cure colic, rheumatism, blindness, and mental illnesses.
Science of sapphire
Sapphire is a form of the mineral corundum, and it exists in a range of colors from light to dark blue. Corundum is the second-hardest mineral after diamond and occurs in a wide variety of colors. Sapphire is any form of corundum that is not red, as red varieties are called rubies. Sapphires can be formed in crystalline limestone, gneiss, schist, and other crystalline rocks. Gem varieties occur chiefly in placer (river gravel) deposits.
*An alterative birthstone for September is lapis lazuli, a rock composed of numerous minerals. Gem varieties of lapis are dark blue, sometimes with white calcite spots within its structure, or specks of pyrite that look like gold.
History of opal
Opals were greatly valued by ancient monarchs for their protective powers. They were worn as jewelry and in crowns to ward off evil and to protect the wearer's eyesight. The opal was also ingested in a ground-up powder to protect against nightmares.
Science of opal
Opal, which is a "mineraloid" (lacking crystalline structure) has a chemistry of primarily SiO2 (quartz) and includes 5%–10% water. The presence of water in the mineral structure allows geologists to determine the temperature of the rock at the time the opal formed. The structure of opal consists of chains of silicon and oxygen formed within tiny spheres. These spheres are usually inconsistent in size and concentration. In precious opals (the variety used most often in jewelry), however, there are many organized pockets of spheres. The spheres diffract light at various wavelengths, creating beautiful, prismatic colors.
*An alternate birthstone for October is variety of tourmaline that has transparent elongate crystals, sometimes pink at one end and green at the other. Tourmaline can also be many tones of pink, green, blue, or even black.
History of citrine
The first civilization thought to wear citrine (a yellow variety of quartz) were the Romans, who shaped it into cabochon—polished but unfaceted cuts of stone worn in jewelry. During the Romantic Period in turn-of-the-century Europe, citrine became more popular for the way it visually enhances gold jewelry. Citrine, like all forms of quartz, was believed to have magical powers and was worn as protection against evil and snake venom poisoning.
Science of citrine
Some citrine actually began as purple amethyst, but heat from nearby molten rock changed it to a warm yellow color. Citrine is one of the less-common varieties of quartz, and it ranges from a pale yellow to a dark amber that's named Madeira for its resemblance to the red wine of Portugal.
*An alternate birthstone for November is yellow topaz.
History of turquoise
Since about 6,000 B.C. when it was first mined by the Egyptians, turquoise has been one of the most valuable opaque minerals in the jewelry business. Native Americans and Persians also valued it for its decorative and ornamental beauty. The Navajo believe that turquoise is a part of the sky that fell to Earth.
Science of turquoise
Turquoise is composed of hydrated copper and aluminum phosphate. It forms when circulating water alters other aluminum-rich rocks in desert environments. Turquoise has a slightly waxy appearance and can range in color from blue to shades of green and yellowish gray. The most valued color of turquoise, though, is the beautiful greenish-blue that contrasts so nicely with precious metals such as silver.
*Alternate birthstones for December are zircon and blue topaz.
Written by Gena Schwam, graduate student, University of Washington Museology Program.