About your gemstones.

Alexandrite is the color-change variety of chrysoberyl: emerald-green in daylight, raspberry-red under incandescent light. The shift is dramatic in the finest stones and subtle in lesser material; quality is judged largely by how distinct and saturated each of the two colors appears in its respective light source.

The gem was discovered in the Ural Mountains of Russia in the 1830s and named for the future Tsar Alexander II, who came of age the same year the first specimens reached the imperial collection. Russian alexandrite from that era set the benchmark by which all later stones are judged.

Alexandrite is one of the recognized birthstones for June, sharing the month with pearl and moonstone, and is the accepted anniversary gemstone for the 55th year of marriage.

Fine alexandrite is rare and seldom encountered in retail jewelry; antique and estate pieces remain an important source of top material. No common treatments are applied — alexandrite reaches the market in its natural state.

Alexandrite is durable enough for daily wear (Mohs 8.5). Clean with warm soapy water and a soft brush. As with any colored gem, protect it from sharp blows and sudden temperature changes.

Commercial sources include Brazil, Sri Lanka, several East African deposits, and limited production from Russia and Myanmar (Burma).

Amber is fossilized tree resin rather than a mineral, placing it (along with pearl and coral) among the organic gems. Its color spans pale yellow, golden honey, deep cognac and reddish brown, with rarer milky-white and almost-black material from some deposits. Amber is so light it floats in saltwater.

Resin began trapping insects, leaves, and the occasional small vertebrate in prehistoric forests tens of millions of years ago; long burial and pressure turned that resin into the gem we know today. Pieces with well-preserved inclusions of extinct species are particularly prized by collectors, both for their beauty and their scientific value.

Humans have worn amber for at least seven thousand years. Carved amber beads have been recovered from Stone Age burial sites, and classical Greek and Roman authors attributed an extraordinary range of medicinal virtues to it.

Amber may be gently warmed during preparation to clarify cloudy material and intensify the dramatic internal stress fractures sometimes called “sun spangles.” This is the only routine treatment.

Amber is soft (Mohs 2.5) and sensitive to chemicals, solvents, and heat. Wipe with a soft cloth only — no ultrasonic, no steam, no jewelry-cleaner solutions, and keep it away from perfume and hairspray.

The most famous source is the Baltic Sea region (Russia, Poland, and the Baltic states); newer important sources include the Dominican Republic and Myanmar (Burma).

Amethyst is the purple variety of quartz, ranging in color from pale lilac to deep, vivid violet. The most prized stones show a rich, even purple with red or blue flashes, sometimes called “Siberian” color regardless of where they were mined.

The name comes from the Greek amethystos, meaning “not drunken.” Ancient Greeks and Romans believed that drinking from cups made of amethyst would prevent intoxication, and the stone was prized as a talisman against ill effects of alcohol. Amethyst was considered a royal stone until large deposits were discovered in Brazil in the 19th century, making it widely available.

Amethyst is the traditional birthstone for February and the accepted anniversary gemstone for the 6th year of marriage. Saint Valentine reportedly wore an amethyst carved with a figure of Cupid.

Most amethyst is not treated, though some is heated to deepen its color or to produce the yellow variety known as citrine. The stone is durable enough for everyday wear but its color may fade with prolonged exposure to strong sunlight.

Clean with warm soapy water and a soft brush. Ultrasonic and steam cleaners are usually safe for untreated amethyst, but avoid sudden temperature changes.

Major sources include Brazil, Uruguay, Bolivia, Zambia, Madagascar and the United States.

Ametrine is a single quartz crystal that contains zones of both purple amethyst and golden citrine in the same stone. The two colors share a sharp boundary inside the crystal, producing some of the most distinctive bicolor gemstones cut today.

The species was discovered in Bolivia in the late 1970s; commercial production began at the Anahí mine, which remains the principal source. Because the bicolor effect is most striking when each color occupies a substantial portion of the cut stone, ametrine is typically faceted in larger sizes — five carats and up is common, and emerald and pear cuts emphasize the color split.

Lacking the deep folkloric history of older gemstones, ametrine has borrowed associations from its parent stones: the calming wisdom attributed to amethyst paired with the warm prosperity of citrine.

Most ametrine is untreated; the bicolor effect is natural, the result of differing iron oxidation states between adjacent zones of the same crystal.

A hard, durable quartz (Mohs 7), ametrine cleans easily with warm soapy water and a soft brush; ultrasonic and steam cleaners are usually safe.

Aquamarine is the sea-blue variety of beryl, the same mineral family that produces emerald and morganite. The most prized stones show a clean, vivid sky-blue to slightly greenish blue, evenly distributed without zoning. Aquamarine forms in larger, cleaner crystals than its emerald cousin, so dramatic statement-sized stones over ten carats are not uncommon.

The name comes from the Latin aqua marina, “sea water.” Ancient mariners regarded aquamarine as a protective talisman, believing it would calm seas and ensure safe passage. The stone has long been associated with youth, hope and clear thinking.

Aquamarine is the birthstone for March and the accepted anniversary gemstone for the 19th year of marriage.

Routine heat treatment removes minor yellow undertones in the rough and stabilizes the pure blue color most buyers expect. The treatment is stable and accepted in the trade.

With a Mohs hardness of 7.5–8, aquamarine is durable enough for everyday wear. Clean with warm soapy water and a soft brush; ultrasonic and steam cleaners are usually safe for clean material.

Significant sources include Brazil, Nigeria, Madagascar, Mozambique and Zambia.

Cat’s-eye chrysoberyl displays a sharp, silvery band of light that floats across the dome of the stone as it is rotated — an optical phenomenon called chatoyancy, caused by parallel needle-like inclusions reflecting light in a single direction. The band opens and closes as the stone is tilted, mimicking the slit pupil of a cat.

The chrysoberyl species also contains the color-changing alexandrite; though chemically related, cat’s-eye and alexandrite look nothing alike. Cat’s-eye is always cut as a cabochon (a smooth dome, not faceted) — faceting would scatter the parallel inclusions and destroy the eye.

Translucent stones in honey-yellow through honey-brown into yellowish-green are the most prized. A sharp, well-centered eye and a high-contrast color combination are the key quality factors.

The gem has long been associated with watchfulness and protection — the “all-seeing eye” regarded as a guardian against ill fortune — and with longevity. There are no common treatments.

With a Mohs hardness of 8.5, cat’s-eye chrysoberyl is among the harder gemstones. Clean with warm soapy water and a soft brush. Avoid ultrasonic and steam cleaners for any stone that shows visible fractures.

Cat’s-eye chrysoberyl is produced primarily in Sri Lanka and Brazil.

Citrine is the yellow to orange variety of quartz, ranging from pale lemon through golden honey to deep madeira red-orange. The finest stones show a saturated, brandy-like orange.

The name derives from the French citron, “lemon,” a nod to its sunny color. Most natural citrine is pale; the deeper oranges and reds typically come from heat treatment of amethyst or smoky quartz — a stable, accepted, and widely disclosed practice.

Citrine is one of the accepted birthstones for November and is the accepted anniversary gemstone for the 13th year of marriage. It has been called the “merchant’s stone” for its supposed power to attract prosperity.

As a hard, durable quartz, citrine cleans easily with warm soapy water and a soft brush; ultrasonic and steam cleaning are also safe. Avoid sudden temperature changes and prolonged direct sunlight, which may slowly fade some heat-treated stones.

Major sources include Brazil, Bolivia, Madagascar and Russia.

Coral is an organic gem produced by colonies of tiny marine animals — coral polyps — that secrete calcium-carbonate skeletons in branching, tree-like colonies. Pieces cut from those skeletons range from semi-translucent to opaque.

White, pink, salmon, red and black are the principal commercial colors. The deepest reds (often called “noble,” “oxblood,” or “blood” coral) are the most valuable. The pale pink material known as “angel skin” is also highly prized.

Coral has been worked since antiquity, particularly in Mediterranean cultures and East Asia. Roman tradition associated it with protection of children and with averting the “evil eye”; Ayurvedic medicine in India includes ground coral powder to this day.

Some commercial coral is bleached for color uniformity, dyed (often pink-to-red), or stabilized with clear polymer. Dyed material may fade in heat or sunlight.

Coral is soft (Mohs 3–4) and chemically sensitive: acids, perfumes, cosmetics, hairspray, household cleaners, and even prolonged contact with skin oils can dull or damage the surface. Wipe with a soft, slightly damp cloth only — never use ultrasonic, steam, or any cleaning solution.

Coral has historically been harvested from the Mediterranean, around Japan and the Hawaiian Islands, and from a number of Pacific reefs. Sustainability concerns have led many appraisers and jewelers to favor older estate material over newly harvested coral.

The name traces to the Greek adamas, “unconquerable” — fitting for the hardest natural substance known. Diamond’s role as the symbol of enduring love reaches back to antiquity, when the stones were variously imagined to be shards of fallen stars, hardened lightning, or splinters of the primal fire.

Diamond is the birthstone for April and the accepted anniversary gem for both the 10th and 60th years of marriage. It remains, by a wide margin, the most popular center stone for engagement rings.

Most diamonds appear colorless to nearly colorless, but rare specimens occur in green, red, pink, blue, yellow, orange, brown and even black. These “fancy color” diamonds carry significant premiums and have their own grading scale focused on the intensity and purity of the color.

Treatments are common in commercial diamond. Laser drilling and fracture filling improve apparent clarity; HPHT and irradiation can alter color. Reputable sellers disclose all treatments — a natural, untreated stone of the same nominal grade is worth more than its treated counterpart.

Despite the highest hardness on the Mohs scale, diamond can be chipped by a sharp blow against a cleavage plane — hardness and toughness are different properties. To clean: a jewelry-cleaner solution, warm soapy water with a soft brush, or a home ultrasonic with its recommended cleaner. A half-and-half ammonia/water soak is also effective for removing the film of skin oils that diamonds attract.

Emerald is the green variety of the mineral beryl, owing its rich color to traces of chromium and sometimes vanadium. The finest emeralds display a pure, vivid green to slightly bluish-green hue, with strong saturation and even color distribution.

The name “emerald” derives from the Greek smaragdos, meaning simply “green stone.” Emeralds have been treasured since at least 1500 B.C., when ancient Egyptian mines produced stones believed to promote eternal life. Cleopatra was famously fond of them.

Emerald is the traditional birthstone for May and is the accepted anniversary gemstone for both the 20th and 35th years of marriage. It is also one of the four “precious” stones, alongside diamond, ruby and sapphire.

Nearly every emerald contains some natural inclusions; the trade lovingly calls these the gem’s “jardin,” or garden. Heavily included emeralds are routinely fracture-filled with cedarwood oil or modern resins to improve their apparent clarity — this treatment is accepted in the trade but is not permanent and may need periodic refreshing by a qualified jeweler.

Because of its inclusions and brittleness, emerald should never be cleaned in an ultrasonic or steam cleaner. Wipe gently with a soft cloth or use lukewarm soapy water and a soft brush. Protect from sharp blows, sudden temperature changes, and harsh chemicals.

Important sources include Colombia, Brazil, Zambia, Ethiopia, Afghanistan and Russia.

Fancy color diamonds occur naturally in yellow, brown, pink, blue, green, orange, purple and the extraordinarily rare red. While most diamonds are graded for the absence of color, fancy color diamonds are graded for the presence of color, with intensity (faint, light, fancy light, fancy, fancy intense, fancy vivid, fancy deep, fancy dark) as the primary value driver.

The most famous diamonds in the world are fancy colors: the deep blue Hope Diamond, the pink Graff Pink, the vivid yellow Tiffany Diamond, the green Dresden Green. Major auction records for any gemstone have repeatedly been set by fancy color diamonds.

Fancy color diamonds share the same April birthstone and 10th- and 60th-anniversary association as colorless diamonds, but their rarity makes them a category of their own.

Some fancy color diamonds are color-treated by irradiation, HPHT (high-pressure, high-temperature) or surface coating; these treatments must be disclosed and are graded separately from natural fancy color diamonds, which command a substantial premium.

Care is the same as for colorless diamond: jewelry cleaner, warm soapy water with a soft brush, or a home ultrasonic with its recommended cleaner. Protect from sharp blows.

Sources include South Africa, Australia (the now-closed Argyle mine produced most of the world’s pinks), Russia, Brazil, India and Canada.

Garnet is not a single gemstone but a family of related minerals, occurring in nearly every color except blue. The most familiar variety is pyrope or almandine in deep red, but garnets also come in vibrant orange (spessartine), bright green (tsavorite, demantoid), pink (rhodolite) and the rare color-changing blue-to-purple (a recent Madagascan find).

The name comes from the Latin granatum, “pomegranate,” because the deep-red crystals resemble the fruit’s seeds. Bohemian garnet jewelry from the 18th and 19th centuries is some of the most prized garnet ever cut.

Garnet is the traditional birthstone for January and the accepted anniversary gemstone for the 2nd year of marriage. Demantoid garnet, with its diamond-like brilliance and unique horsetail inclusions, is among the most valuable garnets and a favorite of fine collectors.

Most garnets are not treated and may be considered “natural” without further qualification, which makes them increasingly desirable in a market full of treated stones.

Clean with warm soapy water and a soft brush. Ultrasonic and steam cleaning are usually safe, though demantoid and stones with prominent inclusions should be cleaned more gently.

Sources include Madagascar, Sri Lanka, Tanzania, Kenya, Brazil, Russia, the United States and Namibia.

Iolite shows a soft violet-blue body color that has long invited comparison with sapphire — but at a fraction of the price. The name comes from the Greek ios, “violet.” The most prized stones display a saturated, even blue without the grayish tint that affects lower-grade material.

Iolite is strongly pleochroic, showing different colors when viewed along different crystal axes — violet-blue from one direction, near-colorless or yellowish from another. Skilled cutters orient the rough to display the strongest blue face-up. Viking navigators reportedly used thin slices of iolite as a natural polarizing filter to locate the sun through overcast skies, well before such optics were formally understood.

Iolite is the accepted anniversary gemstone for the 21st year of marriage. It has no formal birthstone designation.

Iolite is generally not treated. With a Mohs hardness of 7–7.5 it is suitable for everyday wear, though somewhat brittle along its cleavage planes; sharp impacts should be avoided.

Clean with warm soapy water and a soft brush. Ultrasonic and steam cleaners are usually safe for clean stones but should be avoided when prominent inclusions are present.

Major sources include India, Sri Lanka, Tanzania, Madagascar and Brazil.

“Jade” refers to two distinct minerals — jadeite, the rarer and more highly prized variety, and nephrite, the tougher and more common of the two. Both have been worked for thousands of years and both are sometimes carved into pieces of extraordinary intricacy.

Jadeite shows the widest color range, with “imperial” green (a vivid, slightly bluish green) commanding the highest prices. Lavender, white, yellow, orange, red and black jadeite all occur. Nephrite is most often seen in shades of green from creamy white through olive to almost black.

Chinese culture has prized jade — particularly nephrite — for at least six thousand years; in Mesoamerica, jadeite has comparable cultural significance, used in ceremonial and artistic objects well before European contact. Jade is the accepted anniversary gemstone for the 12th year of marriage.

Jadeite is routinely impregnated with a colorless wax or polymer to brighten color and stabilize surface fissures (so-called “Type A” jadeite). More heavily processed material may be acid-treated and polymer-impregnated (“Type B”) or dyed (“Type C”). These treatments must be disclosed; untreated Type A jadeite commands a substantial premium.

Jade is exceptionally tough — possibly the toughest natural material commonly used in jewelry — but not particularly hard. Wipe with a soft cloth; avoid ultrasonic and steam cleaners and protect from harsh chemicals.

Myanmar (Burma) is the principal source of fine jadeite. Nephrite comes from China, Russia, Canada, New Zealand and several other regions.

Kunzite is the pink to lilac-pink variety of the mineral spodumene. Color ranges from delicate baby-pink through a deeper rose to almost magenta in the finest stones. Like several other spodumenes, kunzite is strongly pleochroic, showing different intensities of pink from different viewing directions — skilled cutters orient the rough so the strongest color shows face-up.

The stone was identified and named in 1902 by George Frederick Kunz, the legendary gem buyer for Tiffany & Co. and one of the founding figures of American gemology.

Larger kunzite specimens are surprisingly common; stones over 20 carats are not unusual, and exceptional pieces well over 100 carats exist. The combination of size and saturated pink color makes kunzite a favorite for statement jewelry.

More than half of commercial kunzite has been heat-treated or irradiated to deepen the pink and remove unwanted yellow undertones. The color of some stones may slowly fade with prolonged exposure to direct sunlight or hot display lighting, which is why kunzite is often considered an “evening stone.”

Kunzite is moderately hard (Mohs 6.5–7) but prone to cleavage; sharp blows can cause it to split. Clean with warm soapy water and a soft brush; avoid ultrasonic cleaners, steam, and prolonged strong light.

The principal sources are Afghanistan, Brazil and Madagascar, with smaller production from California (Pala District) and Pakistan.

Lapis lazuli is an opaque, deep blue rock composed primarily of the mineral lazurite, with characteristic flecks of golden pyrite (“fool’s gold”) and occasional white veining of calcite. The most prized material shows a uniform, intense royal blue with sparing pyrite for accent and minimal calcite.

The stone has been worked for at least six thousand years and was particularly valued by the ancient Egyptians, who used it in jewelry, amulets, and as a pigment when ground into ultramarine. Renaissance painters paid extraordinary prices for the same pigment, reserving it for the most important figures in their works.

Lapis is the accepted anniversary gemstone for the 9th year of marriage. It has no formal birthstone designation.

Lapis may be impregnated with colorless wax or oil to brighten its color. Some lower-grade material is dyed to mask calcite or to deepen the blue, and that dye may not be permanent.

Lapis is relatively soft (Mohs 5–6) and porous; wipe with a soft cloth only. Avoid ultrasonic and steam cleaners, perfumes, hairspray, household chemicals, and prolonged contact with skin oils.

The finest historical lapis comes from Afghanistan’s Sar-i Sang mines, which have been producing for thousands of years. Chile and Russia also supply commercial material, typically with more calcite content.

Moonstone is celebrated for its adularescence — a soft, billowy blue or white sheen that floats across the surface of the stone, evoking the light of a full moon. The finest moonstones are nearly colorless with a striking blue sheen against a transparent body.

The name reflects ancient belief that the gem was formed by congealed moonlight. Romans and Greeks associated moonstone with their lunar deities, and Hindu legend describes it as the solidified moonbeams. It has long been considered a stone of love, intuition and emotional balance.

Moonstone is one of the accepted birthstones for June (alongside pearl and alexandrite) and is the accepted anniversary gemstone for the 13th year of marriage.

Moonstone is generally not treated. It is, however, relatively soft (Mohs 6–6.5) and prone to cleavage and brittleness, so it requires gentle handling.

Clean with warm soapy water and a soft brush; avoid ultrasonic and steam cleaners, harsh chemicals, and sudden temperature changes. Protect from scratches and impact.

Major sources include Sri Lanka, India, Madagascar, Myanmar (Burma), and the United States.

Morganite is the pink to peach variety of beryl, the same mineral family as emerald and aquamarine. Its color comes from traces of manganese, ranging from pale, almost watery pink through romantic peach to a deeper magenta in the finest stones.

Morganite was named in 1911 in honor of the American banker and gem collector J. P. Morgan by George F. Kunz, chief gem buyer for Tiffany & Co. Because it commonly occurs in large, clean crystals, morganite is often cut into impressive sizes well over 10 carats.

Morganite does not have an official birthstone or anniversary association, but its rising popularity as a center stone for engagement rings has made it a favorite of modern brides.

Heat treatment is routinely used to remove yellow undertones and produce a purer pink; this treatment is stable and accepted. Untreated peach-colored morganite is also valued by collectors.

With a Mohs hardness of 7.5–8, morganite is durable enough for everyday wear. Clean with warm soapy water and a soft brush. Ultrasonic and steam cleaners are generally safe but avoid stones with prominent inclusions.

Major sources include Brazil, Madagascar, Mozambique, Afghanistan, China and the United States.

Opal is celebrated for its play-of-color — a shifting display of spectral hues caused by tiny silica spheres diffracting light. White opal, black opal, fire opal and boulder opal are the main commercial varieties, with black opal from Lightning Ridge, Australia, generally the most valuable.

The name comes from the Sanskrit upala, “precious stone.” Romans considered opal a symbol of hope and purity, while in some later European folklore it was unfortunately associated with bad luck — a superstition that is wholly unfounded and faded long ago.

Opal is the traditional birthstone for October and is the accepted anniversary gemstone for the 14th year of marriage.

Because opal contains 3% to 21% water and is relatively soft (Mohs 5.5–6.5), it requires extra care. Some opals are stabilized by impregnation with colorless resin to harden them and reduce crazing; doublets and triplets are common assembled stones in which a thin opal slice is backed (and sometimes capped) with a darker material.

Never expose opal to ultrasonic cleaners, steam, or sudden temperature changes — any of these can cause crazing (a fine network of cracks) that permanently damages the stone. Clean gently with a soft damp cloth. Avoid prolonged storage in dry environments.

Australia produces the majority of the world’s precious opal. Ethiopia, Mexico, Brazil and the United States are also important sources.

Pearls are organic gems formed by mollusks — oysters in saltwater, mussels in freshwater — when an irritant within the shell is gradually coated with layers of nacre. Natural pearls form without human intervention; cultured pearls form when a bead or tissue piece is deliberately inserted to initiate the process.

Pearls have been treasured for over four thousand years. They are mentioned in Sanskrit manuscripts, sought by Roman emperors, and carried into modern legend in Coco Chanel’s timeless pearl strands. Today, almost all pearls on the market are cultured.

Pearl is the traditional birthstone for June and the accepted anniversary gemstone for the 3rd and 30th years of marriage.

Pearls are graded on a different system from faceted gems, considering color, luster, surface, shape, size, nacre quality and matching. The major commercial types — Akoya, South Sea, Tahitian, and freshwater — each have characteristic sizes and color ranges.

Pearls are softer than mineral gemstones (Mohs 2.5–4.5) and easily damaged by acids, perfumes, cosmetics and even prolonged contact with skin oils. Wipe gently with a damp soft cloth after wearing. Never use ultrasonic cleaners, steam, jewelry cleaners or harsh chemicals. Store pearls separately from other jewelry to avoid scratches.

The rule “put pearls on last, take them off first” keeps them away from hairspray, perfume and makeup. Restring pearl strands every one to two years if worn frequently.

Cultured pearls are produced primarily in Japan, China, Australia, French Polynesia, Indonesia and the Philippines.

Peridot is the gem-quality variety of olivine, one of the most common minerals in Earth’s mantle but rare in transparent form near the surface. The signature color is a fresh, slightly yellowish green sometimes described as “lime” or “spring leaf.” Some material shows a slightly brownish or olive cast.

Peridot forms deep in the upper mantle and is brought to the surface mainly by volcanism. Tiny grains of peridot can be sifted from the black sand beaches of Hawaii, where lava flows continually deposit fresh olivine. Peridot is also one of the very few gemstones to have arrived on Earth via meteorite.

Peridot is the birthstone for August and the accepted anniversary gemstone for the 16th year of marriage. Folklore credited the gem with protective virtues — it was favored by pirates as a talisman against the “terrors of the night” and used in medicinal preparations in the ancient Mediterranean.

Peridot is generally not treated; what you see is the natural color of the stone. Larger sizes — well over ten carats — are readily available, making peridot a strong choice for statement pieces.

Peridot has a moderate Mohs hardness of 6.5–7 and is somewhat sensitive to sudden temperature changes and household acids. Clean with warm soapy water and a soft brush; avoid ultrasonic and steam cleaners.

Major commercial sources include Myanmar (Burma), Pakistan, the United States (Arizona’s San Carlos Reservation), Egypt’s Zabargad Island, and China.

Rose quartz is the pink variety of quartz, ranging from a very pale, milky blush to a more saturated rosy pink. The pink color is generally caused by traces of titanium, iron or manganese.

Rose quartz has been used decoratively for at least 7,000 years; ancient Egyptians believed it could prevent the signs of aging, and Greek and Roman mythology associate the stone with the gods of love. Today it remains one of the most popular stones for love-themed jewelry.

Rose quartz is the suggested gemstone for the 22nd year of marriage. It has no formal birthstone association but is widely considered a “love stone” of personal significance.

Most rose quartz is untreated. Its color may slowly fade with prolonged exposure to direct sunlight, so display and storage out of strong UV is advised.

With a Mohs hardness of 7, rose quartz is durable enough for jewelry. Clean with warm soapy water and a soft brush; ultrasonic and steam cleaners are usually safe for clean material but should be avoided for stones with significant fractures.

Major sources include Brazil, Madagascar, India, Mozambique, Namibia and the United States.

Ruby is the red variety of corundum, colored by traces of chromium. The most prized rubies show a pure, vivid red to slightly purplish-red — the legendary “pigeon’s blood” of Burma.

The name comes from the Latin ruber, “red.” Ruby has been called the king of gems since antiquity. Ancient Hindus believed that those who offered rubies to Krishna would be reborn as emperors, and early European warriors set rubies into their armor and the hilts of their swords for invincibility in battle.

Ruby is the traditional birthstone for July and the accepted anniversary gemstone for the 15th and 40th years of marriage. With a hardness of 9 on the Mohs scale, ruby is exceptionally durable.

Most rubies are heat-treated to improve color and clarity. Lead-glass filling of surface-reaching fractures is also common in lower-quality material; this treatment is dramatic but not permanent and reduces the stone’s durability and value.

Untreated rubies clean safely with warm soapy water and a soft brush. Treated or fracture-filled rubies should be cleaned only with a soft cloth — never with ultrasonic, steam or chemicals.

The finest historical rubies came from Mogok, Myanmar (Burma). Today rubies are also produced in Mozambique, Thailand, Vietnam, Madagascar, Tajikistan and Tanzania.

Sapphire is the blue variety of the mineral corundum, but the species also occurs in nearly every color of the rainbow except red (red corundum is ruby). “Fancy sapphires” come in pink, orange, yellow, green, purple and the highly prized padparadscha — a delicate pink-orange.

The name comes from the Greek sappheiros, meaning “blue stone.” For centuries sapphire has been associated with royalty, wisdom and divine favor. The famous blue sapphire of Princess Diana, now worn by the Princess of Wales, is one of the most recognized engagement rings in the world.

Sapphire is the traditional birthstone for September and the accepted anniversary gemstone for the 5th and 45th years of marriage. With a hardness of 9 on the Mohs scale, only diamond is harder.

Most blue sapphires are routinely heat-treated to improve color and clarity; this treatment is stable, accepted in the trade, and disclosed by reputable sellers. Some lower-quality stones may be beryllium-diffused to alter color, which is a more aggressive treatment requiring full disclosure.

Sapphire is durable enough for everyday wear. Clean with warm soapy water and a soft brush; ultrasonic and steam cleaners are generally safe for untreated stones but should be avoided for any stone with fractures or diffusion treatment.

Important sources include Kashmir, Sri Lanka, Myanmar (Burma), Madagascar, Thailand and the United States (Montana).

Spinel is one of gemology’s great underappreciated stones — exceptionally clean, brilliant, and available in a wide range of colors. Red spinel resembles fine ruby; pink spinel competes with the best pink sapphires; blue, violet, orange and even color-changing spinels are all known.

Until the 19th century, spinel was systematically confused with ruby. Several of the world’s most celebrated historical “rubies” were eventually revealed to be spinels: the Black Prince’s Ruby and the Timur Ruby — both set into the English Crown Jewels — are the two most famous examples. Even after their reclassification, the trade continued to call such stones “balas rubies” or “ruby spinels.”

Spinel is one of the accepted alternative birthstones for August (a modern addition alongside peridot) and is suggested as the anniversary gemstone for the 22nd year of marriage.

Spinel is generally not treated, which is increasingly rare in a market full of treated stones and adds to spinel’s appeal among collectors.

The stone is hard (Mohs 8) and durable, well suited to everyday wear. Clean with warm soapy water and a soft brush; ultrasonic and steam cleaners are usually safe.

Major sources include Myanmar (Burma), Sri Lanka, Tanzania, Vietnam and Tajikistan.

Sunstone displays a bright, sparkling shimmer called aventurescence, caused by tiny reflective inclusions of hematite or copper. Body colors range from golden yellow and orange through brick red, with the rare green sunstone (such as Oregon sunstone) particularly prized.

The name reflects the gem’s warm, sunlit glow. Ancient legend held that sunstone embodied the rays of the sun and was used by the Vikings as a kind of navigational tool to locate the sun on cloudy days.

Sunstone does not have an established birthstone or anniversary association, though it has become increasingly popular in artisan and one-of-a-kind designs.

Most sunstone is untreated; the natural inclusions that create its aventurescence are part of the stone’s identity. Some lower-grade material may be coated or backed to enhance color.

Sunstone has a Mohs hardness of 6–6.5 and is best protected from sharp blows. Clean with warm soapy water and a soft brush; ultrasonic and steam cleaners should generally be avoided.

Sources include the United States (Oregon), India, Norway, Tanzania, Canada and Russia.

Tanzanite is the violet-blue to bluish-violet variety of the mineral zoisite, prized for its rich color and strong pleochroism (showing different colors when viewed from different directions). The most valued stones display a deep, saturated blue with a purplish flash.

Tanzanite was first discovered in 1967 in the Merelani Hills of northern Tanzania, the only commercial source on earth. Tiffany & Co. named the stone and introduced it to the world, naming it after its country of origin.

Tanzanite is a more recent addition to the official birthstone list for December, joining turquoise and blue zircon. It is also the suggested anniversary gem for the 24th year of marriage.

Nearly all tanzanite on the market is heat-treated to produce or intensify its blue color; the untreated stone is often a brownish purple. This treatment is stable, accepted in the trade, and should be disclosed.

Tanzanite has a hardness of 6.5–7 on the Mohs scale and a tendency to cleave along certain directions, so it should be protected from sharp blows. Avoid ultrasonic cleaners. Clean with warm soapy water and a soft brush.

Because its source is limited to a small area in Tanzania, tanzanite is considered one of the rarer gemstones available.

Most casual buyers picture topaz as a single golden-yellow gem, but it occurs naturally in a remarkable range of colors: orange, sherry brown, red, pink, light green, blue and colorless. “Imperial” topaz — a rich orange-red — and natural pink topaz are the rarest and most valuable varieties.

The name traces to the Greek topazos, an old name for an unrelated yellow gem that may originally have referred to peridot from a Red Sea island. Topaz has been associated with strength, sound mind, and protection against sudden misfortune in folklore traditions spanning several cultures.

Topaz is one of the birthstones for November, alongside citrine. Blue topaz is the accepted anniversary gemstone for the 4th year of marriage; imperial topaz, for the 23rd year.

Almost all blue topaz on the market is irradiated and then heated to produce its color from colorless or pale rough — a stable, accepted treatment that should always be disclosed. Heat treatment is also used to produce pink topaz from naturally brown rough.

Topaz is hard (Mohs 8) but possesses perfect cleavage in one direction, so a sharp blow at the wrong angle can split a stone. Clean with warm soapy water and a soft brush; ultrasonic and steam cleaning are generally avoided, and prolonged exposure to direct sunlight can fade some heat-treated stones.

Sources include Brazil, Pakistan, Nigeria, Sri Lanka, Russia and the United States.

Tourmaline occurs in a broader range of colors than any other gemstone — every shade of red, pink, yellow, green, blue, violet, black, and even multi-colored crystals. Pink-and-green “watermelon” tourmaline is among the most distinctive natural patterns in gemstones. The blue-green Paraíba tourmaline from Brazil shows an electric neon glow due to traces of copper.

The name comes from the Sinhalese turamali, meaning “mixed-colored stones.” Tourmaline was often confused with emeralds and rubies until the 18th century, when it was identified as a distinct mineral.

Tourmaline is the accepted alternate birthstone for October (alongside opal) and the accepted anniversary gemstone for the 8th year of marriage. Pink tourmaline is associated with love and friendship.

Most tourmaline is not treated. Some stones are heated to lighten over-dark colors, and Paraíba tourmalines may be heated to improve their characteristic glow; both treatments are accepted in the trade with disclosure.

Tourmaline is reasonably durable (Mohs 7–7.5) and well suited for jewelry. Clean with warm soapy water and a soft brush. Avoid sudden temperature changes and prolonged heat.

Major sources include Brazil, Nigeria, Mozambique, Madagascar, Afghanistan, Russia and the United States.

Tsavorite is the vivid green variety of grossular garnet, a relative newcomer to commercial gemology. The first deposits were identified in East Africa in the late 1960s, and Tiffany & Co. introduced the gem to the wider world in 1974 under the name “tsavorite,” after Kenya’s Tsavo National Park near the discovery site.

Compared with emerald, tsavorite is harder, more brilliant, and typically far cleaner — most stones are eye-clean rather than carrying the characteristic “jardin” of natural emerald. The most prized color is a saturated, pure green; bluish-green and slightly yellowish-green stones are also common.

Tsavorite is generally not treated, which places it in a small and increasingly desirable category of natural-color gems.

The supply is limited by geology: rough crystals are usually small, and clean stones over three carats are rare. Cut tsavorites over five carats are exceptional and collectible.

Tsavorite is hard (Mohs 7–7.5) and well suited to everyday wear. Clean with warm soapy water and a soft brush; avoid ultrasonic and steam cleaners for stones with visible fractures.

Kenya and Tanzania remain the principal sources; some material also comes from Madagascar.

Turquoise is an opaque, hydrated copper-aluminum phosphate prized for its distinctive blue to blue-green color. The finest pieces show a uniform, vivid sky blue; greener shades — sometimes called “robin’s egg” — and stones with attractive matrix patterning are also valued.

The name comes from the Old French pierre turquoise, “Turkish stone” — a reference to the trade routes through Turkey that brought the gem from Persia (modern Iran) to medieval Europe. Persian turquoise has long set the quality benchmark, though the American Southwest now leads global production.

Turquoise has been worked for at least six thousand years. Egyptian dynasties mined it in the Sinai beginning around 3000 B.C., and Aztec, Inca and Pueblo cultures used it extensively in ceremonial and decorative objects long before European contact.

Turquoise is one of the birthstones for December and the accepted anniversary gemstone for the 11th year of marriage.

A great deal of commercial turquoise is stabilized by impregnation with clear polymer to harden the material and prevent color change from skin oils and chemicals; this is now standard practice. Lower-grade chalky turquoise is sometimes dyed, which is not permanent.

Turquoise is soft (Mohs 5–6) and porous. Wipe clean with a soft cloth only; avoid ultrasonic and steam cleaners, hot water, perfumes, cosmetics, and skin oils as much as practical.

Principal sources today are the southwestern United States (Arizona, Nevada, New Mexico), Iran, China and Tibet.

Zircon is a brilliant, fiery gemstone — sometimes called diamond’s overlooked cousin for its high refractive index and dispersion — that occurs in colorless, blue, yellow, orange, red, green, and brown varieties. Blue is the most popular color in modern jewelry; colorless zircon was once widely used as a diamond substitute, well before the rise of cubic zirconia and moissanite.

The name traces through medieval Latin and Arabic to the Persian zargun, “gold-colored” — a reference to the warm yellow and orange hues known to ancient lapidaries. Folklore credited the stone with protective virtues; medieval travelers carried it as a guard against plague and physical harm.

Zircon is one of the accepted birthstones for December (alongside turquoise and tanzanite).

Most commercial zircon is heat-treated to convert naturally brown or reddish-brown rough into the colorless and bright-blue stones most in demand. The treatment is stable and accepted in the trade.

Zircon is reasonably hard (Mohs 6–7.5 depending on the variety) but its facet edges are prone to abrasion. Clean with warm soapy water and a soft brush; avoid ultrasonic cleaners and prolonged exposure to strong light, which can shift the color of some heat-treated stones.

Major sources today include Sri Lanka, Thailand, Cambodia, Myanmar (Burma) and Tanzania. Zircon is not to be confused with the laboratory-grown cubic zirconia (CZ), which is an unrelated material.