Skip to main content

Gemstone Reference

A visual reference for gemstones and other precious materials.


Search

Fields to search:  


Gemstones

Alexandrite

About: first discovered in Russia in 1830, alexandrite was named after the country's czar at the time, Alexander II.


Considered by many to be an auspicious stone, alexandrite is a special type of chrysoberyl, unique because it changes color depending on the type of light it's exposed to. In daylight, stones appears green or blue-ish green but, under incandescent light, they turn red or reddish-brown.

Colors: green, blue, red, brown, multi-colored

Tags: birthstone, June, transparent, opaque, changes color, chrysoberyl

Amber

About: fans of Jurassic Park know this stone well. Amber is fossilized pine tree resin, typically more than 50 million years old. It is usually yellow or orange in color but has, in rare instances, been discovered in green, red, blue, black and purple. Only about 15% of what is found is appropriate for jewelry.


Trivia tidbit: in November 1716, Frederick William I of Prussia gave Peter the Great of Russia an "Amber Study" to celebrate an alliance between the two nations. Relocated several times, the panels were eventually installed in Catherine Palace (named for Catherine I, Peter's wife). Today's Amber Room is a recreation of the original which was lost at the end of World War II. It took 24 years for craftsmen to complete the recreation and the effect is pretty extraordinary!

Colors: yellow, orange, white, brown, red, green, blue, purple, black

Tags: transparent, opaque

Amethyst

About: amethyst is purple quartz. The depth and degree of the purple color can vary widely from light, rose-like lavender, to deep, dark magenta-esque purple. Regardless of where an amethyst is actually sourced, the term "Siberian" tends to refer to the latter variety, the deeply purple stones.


Translated from the Greek, amethyst (αμέθυστος | améthystos) means, "not drunken," or, "sober," and the stone was originally worn as a talisman against drunkenness - so, an early attempt at controlling hangovers, really!


Amethyst jewelry was especially popular in the late 19th century, but it has adorned humans for more than 5,000 years. Beads, seals and charms made of amethyst discovered in Egypt have been dated back to at least 3100 BC.

Colors: purple

Tags: birthstone, February, quartz, transparent

Ametrine

About: ametrine's name just about gives the game away. It is a two-colored quartz, a combination, both literally and linguistically, of amethyst (purple quartz) and citrine (yellow quartz).


Only available since the late 80s, ametrine is a relative newcomer to the market. It is predominantly found in Bolivia and Brazil.

Colors: purple, yellow, multi-colored

Tags: quartz, transparent

Aquamarine

About: like emerald and morganite, aquamarine is a member of the beryl family.


In its purest form, beryl is colorless, with colored stones resulting from impurities. In the case of aquamarine, which ranges in color from green to blue, the impurity is iron. Stones that tend towards the green end of the spectrum were favored in the late 19th and early 20th centuries. Today, the bluer stones are generally preferred.

Colors: blue, green

Tags: birthstone, March, transparent, opaque, beryl

Bloodstone

About: bloodstone, also known as "heliotrope," is dark green, red-spotted chalcedony. It is the red splatter effect, caused by iron oxide, that gave rise to the stone's name and, in times past, caused it to be viewed as a talisman to stop or prevent bleeding. As a talisman, it would have been placed or worn over the afflicted person's injury. Christians in the Middle Ages believed that the red spots were Christ's blood and, as a result, that the stones were imbued with special powers. More recently, it has been a popular choice for men's rings.

Colors: green, red, multi-colored

Tags: birthstone, March, opaque, spotted, chalcedony

Carnelian

About: carnelian is chalcedony that is reddish or orange in color, thanks to iron oxide. It has been used by humans for thousands of years - for amulets, cabochons, beads, cameos and carvings, among other precious items. Indeed, it is believed the Prophet Muhammad wore a signet ring with carnelian in it. Several centuries later, Napoleon purportedly carried with him an octagonal carnelian seal that he personally seized during his campaign in Egypt, later passing it onto his nephew and heir, Napoleon III.

Colors: orange, red, brown

Tags: chalcedony, translucent, opaque

Citrine

About: another member of the quartz family, citrine is typically yellow but can also be orange, or brown in color. Natural instances of the gem tend to be rare and a lot of commercially available stones are in fact heat-treated amethysts. Citrine's name derives from the same root as citrus - or, citron, the French word for lemon.

Colors: yellow, orange, brown

Tags: birthstone, November, quartz, transparent

Diamond

About: the hardest mineral on earth, this is probably the gemstone that needs the least amount of introduction.


Several thousand years ago, and for the majority of the time since, India was the world's main source for diamonds. That changed in 1725 when diamonds were discovered in Brazil, a discovery that eventually saw Brazil eclipse India as a source. Around 1866, sourcing shifted yet again when kimberlite diamonds were first discovered in South Africa.


For roughly a century, South Africa dominated the diamond trade. Today, however, many countries supply the market, including (but not limited to): Russia, Botswana, Congo, Canada and Australia. Australia, for example, produced 1/3 of the world's diamonds in 1998, although only about 5% were of gemstone quality. Roughly 45% were used for more affordable jewelry and 50% were suitable only for commercial purposes.


Most folks are familiar with colorless or clear diamonds, but this gemstone actually occurs in a wide range of colors, yellow being the most common. That said, deep purple, blue, red, green and yellow stones are rare and, as a result, tend to command high prices.

Colors: colorless, yellow, orange, brown, black, gray, pink, purple, green, blue, red

Tags: birthstone, April, transparent, opaque

Emerald

About: emerald is the most famous gemstone in the beryl family. Only the best emeralds are transparent - and there appears to be some debate as to what constitutes a 'true' emerald - whether stones that get their color from vanadium count, or whether beryl colored by chrome is the only stone that can be properly called an emerald. Regardless, it is difficult to find a flawless emerald, perhaps because all are relatively brittle.


There is some evidence that emeralds may have been mined in Egypt as far back as 3500 BC. Today, those mines have been exhausted or do not yield high quality gems - instead, Colombia is generally considered to be the premier source for new emerald finds. Often, emeralds are cut in steps with abbreviated corners - so much so that this has come to be known as the "emerald cut." This tends to preserve more of the stone and, at the same time, the minimization of sharp corners helps to protect this more delicate gem from damage.

Colors: green

Tags: birthstone, May, beryl, transparent, opaque

Garnet

About: historically, garnets have been associated with friendship. Purportedly, wearing one (or many) of the stones improved one's relationships with others, an effect that was further amplified if the wearer was born in January.


Most well known are red garnets - called pyrope (light to dark red) and almandine (typically an even darker red, sometimes verging on black or purple) - but garnets actually come in a wide array of colors. Especially popular in Europe in the 18th and 19th centuries, garnet is another gemstone that humans have used for millennia to adorn themselves.

Colors: red, green, yellow, orange, brown, pink, purple, black

Tags: birthstone, January, transparent, opaque

Hematite

About: although predominantly black, gray or brown in color, when hematite is cut in thin slices, it turns red and can be transparent. This explains the stone's name which derives from αίμα, the Greek word for "blood." It explains too why it is known as "bloodstone" in some countries, a term which can lead to some confusion as, in English, that term refers instead to a kind of chalcedony (see bloodstone).


In some instances, this stone can have a mirror-like, reflective aspect. When that happens, it is referred to as "specular" hematite. It is also possible for the stone to present with iridescence, in which case it's called "rainbow" hematite.


Historically, hematite has been used for mourning jewelry. It is rarely used for earrings as it is fairly dense and therefore heavy. More commonly, it is used for necklaces, rings and carvings.

Colors: black, gray, brown, red

Tags: opaque, transparent, iridescent

Iolite

About: also known as "cordierite" and "dichroite," iolite typically falls somewhere on the blue-purple color spectrum. As a result, it has often been used as a sapphire or tanzanite substitute. In contrast to sapphire, however, iolite has a crystal structure that means the color perceived by the viewer depends on their position in relation to the stone. Typically, iolite might look dark blue or violet-blue from one angle, appear gray, yellow-ish or colorless when viewed from another, and pale blue from yet another angle. Occasionally iolite will present with a reddish cast or "aventurescence" (a glitter-like effect).


An interesting factoid - apparently, on foggy or hazy days, Vikings used iolite as a light polarizer. They would hold a thin slice of the stone to the eye and it would cancel out some of the interference from the haze or mist, allowing for more precise orientation to the sun. As a result, iolite is sometimes referred to as the "Viking's compass."

Colors: blue, purple, brown, yellow, red

Tags: transparent, translucent

Jade - Nephrite

About: known for thousands of years in China as yu, the term "jade" emerged in the 16th century and is credited to the Spanish conquistadors. Both terms were unknowingly used to refer to what are in fact two minerals that look very similar.


It is believed that the initial discovery, that jade was in fact two minerals and not one, was made by the Chinese in the 18th century when they began importing jadeite jade from Myanmar. Up to that point, the Chinese had only had access to nephrite jade, white being the color most prized by the country's royalty. In 1863, a French mineralogist, Alexis Damour, formalized the distinction between the two in the West. He used the Roman name for jade, "nephrite," to refer to one and introduced the term "jadeite" to refer to the other.


Both nephrite and jadeite are tough stones that are difficult to break and/or chip, with nephrite being the slightly stronger of the two. That, in addition to its greater availability, may be why it was used for both weaponry and tools in prehistoric times - for example, for arrows and axe heads. According to one source we came across, nephrite is in fact stronger than steel!


In pre-Columbian Central America, nephrite jade was primarily sourced from Guatemala and was more highly valued than gold. Today though, China is perhaps the country most famously associated with jade, specifically nephrite, as it has a long, uninterrupted history of admiration for and use of the mineral. Indeed, it was often used for religious carvings and was worn by persons of high rank. China remains the primary center for carving although nephrite is now used all over the world for cabochons, jewelry and vases.


A final side note - jadeite has a more granular crystal structure than nephrite which means it is only possible to find examples of the cat's eye phenomenon in nephrite.

Colors: green, gray, white, black, brown, yellow, beige

Tags: opaque

Jade - Jadeite

About: in 1863, Alexis Damour, a French mineralogist, affirmed that what had been known as "jade" was, in fact, two different minerals. He introduced the term "jadeite" and recycled the word "nephrite" (the Roman word for jade) to distinguish the two.


Jadeite is a bit denser and harder than its counterpart and can therefore be polished to a higher sheen. As well, it is the rarer of the two jades, with the most valuable examples typically coming from Myanmar (aka Burma). Around 1750, China began importing jadeite from Myanmar and it is believed that it was then when the distinction between the two jades was first discovered.


The purer the color, the more valuable the jade and, all else being equal, green is the most valued color today, followed by purple. "Imperial jade," the most valuable jade of all, is translucent jadeite that is emerald or apple green in color.


Side note: unlike most other minerals which are formed from a single crystal, nephrite and jadeite are comprised of interlocking crystals. On balance, jadeite is made up of coarser crystals than nephrite, sometimes to the point where they are visible to the naked eye.

Colors: green, purple, white, gray, yellow, orange, brown, red, black

Tags: opaque, translucent

Jasper

About: there seems to be some discussion as to how exactly to classify jasper. Sometimes it is grouped under the chalcedony umbrella - at other times, it is considered to be a group unto itself within the quartz family.


It is perhaps easy to understand this ambiguity as jasper comes in a wide range of colors and patterns. Uniform coloration is the exception rather than the rule. More often than not, jasper is spotted or striped. This is thanks to the fact that any given piece of jasper will contain up to 20% foreign matter, matter that determines the stone's color and patterning.


Jasper is found all over the world and, because of its often unusual patterning, offers a lot of scope for innovative designs. Historically, jasper has been used for cameos and intaglios. Today, it is more commonly used for cabochons, ornaments and mosaics.

Colors: red, yellow, green, brown, white, gray, black, pink, blue

Tags: opaque, chalcedony, quartz, striped, spotted, patterned

Kunzite

About: kunzite is a fairly recent addition to the gem canon and refers specifically to spodumene with a pale pink or pale purple hue imparted by manganese.


The first example of spodumene was discovered in Brazil in 1877 and the first example of kunzite spodumene was discovered in California in 1902. The stone was eponymously named after George Frederick Kunz, a mineralogist and, at the time, vice president of gemology at Tiffany & Co.


Kunzite is generally light in hue with darker-hued examples tending to be correspondingly more expensive. It should be mentioned that kunzite may lighten over time as it has the potential for fading. It is also worth noting that it is a fairly fragile gemstone, susceptible to chipping, making it perhaps more suitable for special occasion, rather than every day wear.

Colors: pink, purple

Tags: spodumene, transparent

Labradorite

About: first discovered on the Labrador peninsula in Canada, and eponymously named, labradorite is a type of feldspar that is generally dark in color, ranging from dark gray to gray-black. Yellowish-brown, red, orange, white, and colorless examples have also been found but they are less common.


Labradorite often presents with something called "labradorescence." In the darker stones, this is usually observed as a flash of blue but sometimes it manifests in green, yellow, orange or, less commonly, purple flashes. White or colorless labradorite can exhibit multi-colored labradorescence and, in those instances, is sometimes referred to as "rainbow labradorite."

Colors: gray, black, brown, yellow, colorless, white, red, orange

Tags: feldspar, transparent, opaque, iridescent

Lapis Lazuli

About: technically, lapis lazuli is a rock and not a mineral - and, like most rocks, it is in fact composed of two or more minerals. Regardless, it has long been grouped with pure minerals as a gem, and prized for adornment and jewelry.


Lapis lazuli gets its blue color from sulfur. Due to its hodgepodge make-up, however, quality and characteristics of individual stones can vary widely. Generally, deep blue lapis lazuli with flecks of white (calcite) or yellow (pyrite) is the most prized.


Used by humans for millennia, lapis lazuli has been mined in the Hindu Kush mountains for more than 6,000 years, a location that continues to yield the highest quality stones. Lapis lazuli from Afghanistan has been used in many well-known pieces of jewelry and art, among them Tutankhamen's death mask, where it was used to outline the pharaoh's eyes and for his eyebrows. Today, other large-scale sources of lapis lazuli include Russia and Chile.


In the past, lapis lazuli had a wide variety of applications. It was used to decorate palaces and churches and, as it is today, in jewelry. As well, it was ground up and used as eyeshadow and for medicinal purposes. From the 6th century, artists also used ground lapis lazuli to make a blue pigment called ultramarine.


Ultramarine was very expensive and much prized on the painter's palette, especially during the Renaissance - so much so that it was often reserved for special subjects such as the Virgin Mary or Jesus. Notable examples of its use are the head scarf in Vermeer's Girl with a Pearl Earring, and Jesus' clothing and that of several of his disciples (though noticeably not Judas who was demoted to blue azurite) in Leonardo da Vinci's The Last Supper.


Eventually, synthetic pigments replaced ultramarine and, these days, lapis lazuli is most commonly used for rings, necklaces, watch dials, vases, small sculptures and other such ornaments.

Colors: blue

Tags: birthstone, December, opaque

Moonstone

About: moonstone is a type of feldspar that is most commonly white, colorless or light gray-blue in color. The most valuable examples are blue, verging on transparent.


Moonstones are prized for their "schiller" or "adularescence," a kind of blue or white shimmer that appears to emanate from beneath the surface of the stone. In India, moonstones were once believed to contain captured moonlight. Whether or not this is what led directly to the stone's name, it certainly helps one understand the reasoning behind it.


Today, Sri Lanka, Myanmar (Burma) and India are the premier sources for moonstone. Most commonly it is cut into cabochons.

Colors: white, colorless, gray, blue, pink, yellow, orange, brown, green

Tags: birthstone, June, feldspar, transparent, opaque, iridescent

Morganite

About: like emerald and aquamarine, morganite is a type of beryl. Essentially, morganite is pink-, rose-, peach- or violet-hued beryl that gets its coloring from manganese impurities. Morganite is dichroic which means that it may display a hue (pink or violet) from one angle and appear colorless from another.


It is not uncommon for morganite to be heat treated to intensify coloration - or, in the case of a stone with a yellow or orange cast, to improve the tone of the pink color. Brazil and Madagascar are considered to be the most important sources for top-of-the-line stones.


Morganite was named for J.P. Morgan, the American banker, who was apparently quite a gem collector. Incidentally, G.F. Kunz, vice president of gemology at Tiffany & Co. and the man for whom kunzite is named (see kunzite), helped Morgan assemble his first collection.

Colors: pink, orange, purple

Tags: transparent, opaque, beryl

Mother of Pearl

About: mother of pearl or "nacre" is the interior, iridescent lining of a mollusk or snail shell. Nacre is actually comprised of the same materials as pearls but is considerably cheaper. It is easy for jewelers to work with and is commonly used for buttons, clock faces, cabochons, beads, costume jewelry, and inlay work (such as pistol and flatware handles).


Not surprisingly, pearl farms are the predominant suppliers of mother of pearl. Most pearl farms raise mollusks that have a white nacre. Tahitian and South Sea pearl mollusks are an exception to this rule, presenting with a dark nacre.


Another source for mother of pearl is the Pāua (Haliotis australis), a type of edible sea snail or abalone found in New Zealand that displays a blue-green iridescence. The Māori people there have a long tradition of using Pāua nacre for inlay work and carvings. Abalone shells are also used in the United States and South Africa to source mother of pearl, while conch shells are used in the Indo-Pacific region.

Colors: white, pink, blue, purple, gray, brown, yellow, beige, black, rainbow, multi-colored

Tags: opaque, iridescent

Obsidian

About: obsidian is most familiar as a black stone - indeed, poets and writers often reference it when attempting to describe a depth and degree of blackness. That said, obsidian also exists in shades of gray, brown, green, blue and even red, the rarest of all the colors.


Obsidian is actually a kind of natural glass, formed when lava cools rapidly enough to inhibit crystallization. Stones can be uniform in color, striped or variously patterned. Snowflake obsidian is black or dark gray obsidian with white, snowflake-like spots that are the result of air bubbles or crystallites. Some obsidian presents with iridescence.


Because it is formed through volcanic activity, current sources for obsidian are not surprising: Ecuador, Java, and Hawaii, among other locations. Obsidian is a material that has long been used by humans - in prehistoric times, for weaponry, tools, masks, adornment, and the like. Today, thanks to its prevalence, it is an inexpensive option for jewelry.

Colors: black, gray, brown, green, blue, red

Tags: transparent, opaque, iridescent

Onyx

About: there is some confusion surrounding the term "onyx" as it is often used to refer to solid black stones which are, in fact, dyed agate or other types of chalcedony. True onyx is, in its natural state, a type of layered chalcedony that has a black or brownish-black base and white banding. Agate is considered to be related, the key difference between the two being that agate often presents with curved or concentric banding, while onyx typically has straight or parallel bands.


As far back as ancient Egypt, the practice of dying onyx (and agate) has been known and employed to alter or further showcase coloration of stones. As mentioned above, stones that are uniformly black and are called "onyx," are typically dyed chalcedony. True onyx, complete with white bands, is often imitated too using dying methods.


Onyx was particularly popular in ancient Rome and in subsequent centuries for seals, both in standalone and ring form. The seals were often carved quite artistically, showcasing the stone's natural banding in the relief-work. Because of the layered effects one can achieve, onyx has also been popular for cameo work, such as in this example held at the Museum of Fine Arts, Boston. Today, onyx is often used for beads and cabochons.

Colors: black, brown, white, multi-colored

Tags: opaque, striped, chalcedony

Opal

About: prior to doing our research, we were almost solely familiar with white opals. As a result, it was a surprise to discover the range and variety of naturally colorful opals that are in fact out there - from aqua, to red, to yellow, to blue, to mosaic-like, patterned opals.


Opals are typically divided into two sub-groups: precious opals (iridescent) and common opals (not iridescent). Depending on who you ask, sometimes fire opals (opals ranging in color from yellow to red that are occasionally iridescent) are split out as a third group.


Opals are formed from hardened silica gel. However, even though they feel rock-solid, opals are made up of somewhere between 3-30% water which means they can in fact dry out over time, increasing the potential for cracking. Measures can be taken to discourage dehydration but it is something worth highlighting in advance of any purchase as it distinguishes the opal from most other gems which are crystalline (not made from silica gel) and therefore don't run the same risk.


High quality opals tend to be transparent, not milky, and exhibit iridescence of good intensity and breadth of color. "Harlequin opals," transparent or translucent opals with mosaic patterns in blue or green, are among the most valuable. The cat's eye phenomenon, also known as chatoyancy, is rare in opals but, when it is found in large stones, it is much sought after.

Colors: clear, white, blue, gray, aqua, red, yellow, green, orange, rainbow, multi-colored

Tags: birthstone, October, transparent, opaque, iridescent, patterned

Pearl

About: most pearls come from saltwater oysters (mollusks in the Ostreidae family), but certain types of freshwater mussels and a few other types of shellfish are also capable of producing pearls. On balance, saltwater pearls tend to be more uniform in shape and more highly valued than their freshwater counterparts.


Once believed to the tears of the gods, pearls are in fact formed when foreign matter gets into an oyster (or other pearl producing mollusk), lodging in the mollusk's mantle, or between its shell and mantle. The mantle is the part of the mollusk that secretes mother of pearl and builds up the shell. Foreign matter caught up in this "spray painting" gets coated too, resulting in a pearl. Sometimes in the course of creation, the pearl gets stuck to the shell. When this happens, it is called a "blister" or "shell" pearl.


Pearls vary widely in size, ranging from the size of a round sprinkle or nonpareil, to egg-sized (see, for example, the Hope Pearl, believed to be a blister pearl). In terms of color, white predominates but other colors are possible. Coloration depends on the type of mollusk making the pearl and the water it lives in.


Pearl-producing mollusks thrive in warmer waters such as the Persian Gulf, a source particularly famous for its white and pink pearls. Similarly, the Gulf of Manaar in the Indian Ocean has long been known for its yellow and pink-red seed pearls. Madagascar, Myanmar (Burma), the Philippines, northern Australia and various islands in the South Pacific are also noted sources for natural pearls.


Today, however, cultured pearls dominate the marketplace, accounting for approximately 90% of pearls bought and sold. Cultured pearls are not fake or imitation pearls, but rather pearls created with human assistance, a practice that arose in response to high demand and decreasing availability of natural pearls (due to pollution and over-harvesting). Japan is particularly renowned for its cultured pearl production.

Colors: white, pink, gray, yellow, green, purple, blue, black

Tags: birthstone, June, translucent, opaque

Peridot

About: also known as "chrysolite" and "olivine," peridot numbers among the gemstones that have been mined by humans since ancient times, when the stone was purported to protect its wearer from evil spirits. The term "olivine" is typically used to refer to any instances of the mineral whereas "peridot" is generally used to refer to gem-quality stones.


The most prized examples of peridot have excellent clarity and a beautiful green color. Stones can sometimes have a yellow or brownish cast - the more pronounced this is, the less desirable they tend to be.


Zabargad Island in Egypt was, for a long time, a rich source of high-quality peridot. Indeed, the largest peridot found to date comes from Zabargad. Currently held at the Smithsonian National Museum of Natural History, it weighs just over 62 grams, or 2 ounces. Today, Pakistan and Arizona are two of the main sources for peridot.


Side note: it is with thanks to peridot that we discovered there is such a thing as extraterrestrial gemstones! Needless to say, space-sourced peridot is extremely rare. The first known example was found in the Krasnoyarsk meteorite, also known as "Pallas's Iron" (Палласово железо), discovered in 1749 and currently held at the Fersman Mineralogical Museum in Moscow, Russia.

Colors: green

Tags: birthstone, August, transparent

Rose Quartz

About: rose quartz ranges in color from very pale pink, to peach-colored, to deep pink. It is typically translucent and is often used for cabochons, beads and decorative carvings. Transparent examples of rose quartz are rare and may be faceted.


Rose quartz tends to be brittle and its color can fade over time. Currently, Madagascar seems to be viewed as the premier source for quality stones.

Colors: pink

Tags: translucent, transparent, quartz

Ruby

About: historically, rubies have been among the most expensive gemstones in the world. At times, such as at the end of the 19th century, they were in fact the most expensive.


Ruby is one of two kinds of the corundum species used for making jewelry - the other is sapphire. Rubies present in varying shades of red and have historically been confused with red garnet and red spinel, a clear distinction between them only being made as late as 1800 (or thereabouts).


Color and intensity vary with each new find and cannot be used as a reliable indicator for a ruby's provenance. A stone's inclusions may in fact be more indicative. "Pigeon's blood" is considered to be the most desirable color for a ruby - red with a suggestion of blue. One source we consulted likened this color to, "glowing coal or the red of a traffic light."


Large rubies are found less frequently than large diamonds. Occasionally, examples are discovered that present with asterism (a six-pointed star effect) or, in rare instances, with the cat's eye effect. The Rosser Reeves Star Ruby, found in Sri Lanka and held at the Smithsonian National Museum of Natural History, is believed to be the largest star ruby in the world.


Corundum is the second hardest gemstone after diamond but it is typically brittle, so rubies must be cut and set with care. Once set, however, they can take a good amount of wear and tear. Sources for high-quality stones include Myanmar (Burma), Thailand, Sri Lanka and Tanzania.

Colors: red

Tags: birthstone, July, corundum, transparent, opaque

Sapphire

About: sapphire is one of two kinds of the mineral corundum used for making jewelry - the other is ruby. Unlike ruby, however, which only exists in the color red, sapphire occurs in many different colors. In fact, all gem-quality corundum that is not red is generally referred to as "sapphire."


Blue is the most famous (and most prized) color for sapphires. As such, convention dictates that, unless a stone is blue, its color should be specified, for example, "yellow sapphire." It's also worth mentioning that some sapphires display different colors in natural as opposed to artificial light.


Iron and titanium are what make blue sapphires blue. Because there is greater prevalence of these impurities globally, sapphire is more common than ruby. Still, large examples are rare. The Star of India, held at the American Museum of Natural History in New York, is the largest cut, gem-quality, star sapphire in the world.


Corundum is the second hardest gemstone after diamond but it is typically brittle, so sapphires must be cut and set with care. Once set, however, they can take a good amount of wear and tear. Historically, Kashmir was considered the premier source for sapphire but deposits there appear to have been largely exhausted. Today, Myanmar (Burma), Sri Lanka and Thailand number among the most important sources for high quality stones.

Colors: blue, pink, orange, yellow, green, purple, black, colorless

Tags: birthstone, September, corundum, changes color, transparent, opaque

Sardonyx

About: sardonyx is essentially a combination of sard and onyx, both of which are forms of chalcedony. Sard is reddish-brown or orange-brown, whereas onyx is black with white banding. Sardonyx inherits the reddish- or orange-brown coloring of sard but differs from it in that it also presents with the white bands of onyx.


As with sard and onyx, sardonyx has historically been used for seals, intaglios and cameos, such as in this example held at the Museum of Fine Arts, Boston. Today, sardonyx is commonly used for cabochons and beads.

Colors: brown, red, orange, white, multi-colored

Tags: birthstone, August, striped, chalcedony, opaque

Sodalite

About: sodalite presents in many different shades of blue and is itself a significant component of lapis lazuli, a stone renowned for its rich blue color. When pink sodalite is found, it is often called "hackmanite." White patches of calcite are common in both the blue and pink stones.


Sodalite is regularly used for necklaces, cabochons and other decorative purposes. It is worth noting, however, that the stone's color can fade in response to light exposure. Canada has large deposits of sodalite and is the world's primary source.

Colors: blue, pink, white, multi-colored

Tags: transparent, opaque

Spinel

About: in mineralogy, spinel is actually quite a broad classification, encompassing a whole group of minerals. Few, however, are considered to be of gemstone quality. Those that are present in a wide range of colors.


Red spinel (along with red garnet) was once confused with ruby. Presumably furthering that confusion is the fact that spinel is typically found in spots where ruby and sapphire may also be present - indeed, the discovery of spinel is oftentimes a bonus byproduct of searching for the other two.


Many of the world's most famous "rubies" turned out to be spinels once the scientific distinction was made. Not all red spinels can be mistaken for rubies but some can and they offer a more affordable alternative for those looking at red stones. Large stones are rare and star spinel exceedingly so. Red remains the most popular color for spinel.

Colors: red, orange, yellow, brown, blue, purple, green, black

Tags: transparent, opaque

Sunstone

About: sunstone presents as if imbued with glitter. Typically, the glitter effect is red, reddish-orange or reddish-yellow but blue or green are also possible. The stone itself sits somewhere along the orange-red-brown spectrum. On occasion, sunstone will exhibit an almost metallic look, akin to bronze. Asterism is also possible in the form of a four-pointed star.


First discovered around 1700, sunstones are cut both as cabochons (when opaque) and in faceted shapes (when transparent - or nearly so). Deposits of sunstone are to be found globally, from India, to Norway, to the United States.

Colors: orange, red, brown

Tags: feldspar, translucent, opaque

Tanzanite

About: eponymously named for Tanzania, where it was first discovered in the 1960's, tanzanite is gemstone-quality zoisite colored by vanadium. It presents in varying shades of blue and purple, and typically appears more purple-ish in artificial light. Sometimes "tanzanite" is used to refer to other types of gem quality zoisite but, if so, the term is generally prefixed by the color of the stone so, for example, "green tanzanite."


Generally, tanzanite that tends towards the blue end of the blue-purple spectrum is more highly valued. Based on appearance alone, tanzanite can, in some instances, be mistaken for sapphire. However, tanzanite is a softer stone with a brittleness that means it chips more easily than its doppelgänger. For this reason, tanzanite may be more suitable for necklaces and earrings, or for rings that are not worn on a daily basis. Most stones are heat treated to enhance color and/or eliminate hints of green, gray or brown. Tanzania remains the only source for its namesake.

Colors: blue, purple

Tags: birthstone, December, transparent, changes color

Tiger's Eye

About: tiger's eye is a form of chatoyant or cat's eye quartz that is brown or brown-black with yellow-brown stripes. It is closely related to hawk's eye which is blue-black or greenish-black in color. The two variations are typically found near (or even next to) each other. Stones that are red will have been dyed and are referred to as ox's eye.


Tiger's eye is often used for costume jewelry and decorative objects. Cabochons are popular too as the cut flatters the stone's chatoyancy.

Colors: yellow, red, brown, green

Tags: opaque, quartz, striped

Topaz

About: in its natural state, topaz is most commonly light brown, turning colorless with light exposure. Natural yellow, orange, red, and pink stones are rarer and more prized as a result. When color is present, it tends to be on the paler side relative to other gems of the same hue. For this reason, and to expand the range of colors on offer, topaz is often treated, with the aim of intensifying or changing a given stone's color.


Large examples of topaz are more common than with other gems. Most prized are naturally occurring pink stones and "imperial topaz," yellow or orange stones with hints of pink or red. The more intense the color, the more desirable (and the more expensive) the stone. Other colors can be much more affordable but it is worth noting that some, such as brownish-yellow, are prone to fading.


A final note - the term "topaz" has historically been used quite flexibly. In fact, up until the 18th century, most yellow stones, regardless of species, were referred to as topaz. Today, some remnants of these loosey-goosey naming practices linger, so, when considering a topaz, be sure to ascertain it is in fact the genuine article.

Colors: colorless, yellow, orange, pink, brown, red

Tags: birthstone, November, transparent, translucent

Tourmaline

About: tourmaline is a group of stones that have the same crystal structure but, thanks to different impurities, occur in a wide range of colors. Indeed, some stones have more than one color - a good example being "watermelon tourmaline" which presents with a pink center and green edge. Tourmaline that exhibits the cat's eye phenomenon is rare, as are stones that have color changing properties.


Black tourmaline was once used for mourning jewelry but is less in demand these days, with multi-colored, green, blue, pink and red stones picking up the slack. Tourmaline is cut both in cabochon and in faceted form.


A curious little scientific tidbit - when one end of a tourmaline stone is pressed, or when the stone is heated, it acquires an electrical charge. In this state, it attracts or repels things like dust and ashes, featherweight and non-metallic matter.

Colors: colorless, multi-colored, pink, red, yellow, brown, green, black, blue

Tags: birthstone, October, transparent, opaque

Turquoise

About: brooches, necklaces, bracelets, cabochons and decorative carvings made out of turquoise have been popular for millennia. Indeed, turquoise is believed to be one of the first gemstones mined by humans with deposits in Sinai, Egypt exhausted as early as 2000 BC.


The most prized turquoise is generally sky blue, although, in some places, there may be a preference for greener shades. Persia (now Iran) has historically been the source for the most sought after blue turquoise, having been mined there for more than 3,000 years. Iranian deposits are pretty much spent these days but, originally, Persian turquoise made its way to Europe via a trade route through Turkey. It is believed that this is where the stone gets its name, with "turquoise" translating as, "Turkish stone."


The above picture shows a piece of turquoise with a significant amount of black veining. This type of patterning tends to reduce the value of a stone and a premium is given to pieces without lines or "spider webbing." High levels of porousness too can reduce the value of turquoise. Finally, it should be noted that some turquoise may change color after it is mined, turning green, white or even brown.


Here in the States, Arizona and New Mexico are rich in turquoise and, if you travel to either state, chances are good that you will see a wide range of turquoise jewelry for sale. In addition to the southwest of the United States, turquoise is also sourced from Afghanistan, Australia, and Mexico, among other countries.

Colors: turquoise, blue, green

Tags: birthstone, December, translucent, opaque

Zircon

About: zircon seems to have a bit of a PR problem. Because of its name, it's often confused with cubic zirconia, a lab-created, synthetic stone. To be fair, some of the confusion may arise from the fact that, before cubic zirconia came along, zircon occasionally did duty as a diamond substitute. Zircon is in fact naturally occurring and it presents in a range of colors.


Grayish-brown and reddish-brown zircon is most common in nature but heat treatments are often employed to alter coloration. Natural, yellowish-brown zircon is generally the most prized while a greenish cast may signal decay, indicating a weaker or less durable stone.


Like diamond, zircon tends to have a wonderful brilliance. However, it is not as hard as its counterpart so, in older pieces of jewelry, it is sometimes possible to distinguish zircon from diamond by a tell-tale softening or wearing of faceted edges.

Colors: colorless, yellow, orange, blue, red, brown, purple, green

Tags: birthstone, December, transparent, translucent

Sources

This reference offers only a cursory look at each stone. For more details, be sure to check out one (or more!) of our sources.
There's a ton of fascinating information we just couldn't fit here - including advice and insight for prospective buyers.

Books

Crowe, Judith. The Jeweler's Directory of Gemstones: A Complete Guide to Appraising and Using Precious Stones, from Cut and Color to Shape and Setting. Buffalo, NY: Firefly (U.S.), 2006. Print.

Hall, Cally. Gemstones. 2nd ed. New York, NY: Dorling Kindersley, 2002. Print.

Newman, Renée, GG. Gemstone Buying Guide: How to Evaluate, Identify, Select and Care for Colored Gems. 2nd ed. Los Angeles, CA: International Jewelry Publications, 2003. Print.

Schumann, Walter. Gemstones of the World. 5th ed. New York, NY: Sterling, 2013. Print.

Magazines

"The Future of Forever." The Economist 25 Feb. 2017: 50-52. Print.

Images

Licensed from: Bigstock.com