Tourmaline is one of the most colorful gemstones. It got its name at the beginning of the 18th century when Dutch sailors brought gems that natives of Sri Lanka called turamali. Turmaline is a relatively hard material 7-7.5 on Mohs scale suitable for use in jewelry. Tourmalines include a whole group of minerals with a common crystalline structure but with different chemical compositions.
Iron-rich tourmalines are usually black to bluish-black to deep brown. At the same time, magnesium-rich varieties are brown to yellow, and lithium-rich tourmalines are almost any color: blue, green, red, yellow, pink, etc. Tourmaline is rarely colorless. The most valuable varieties of tourmaline are:
- Paraiba – read full article
Garnet hardness on the Mohs scale is approximately 7- 7.5 – well suited for use in jewelry. Most garnets are clear from inclusions. Due to their relative hardness and clarity, most garnets can be faceted. Garnets occur in all colors except blue
The name ‘garnet’ comes from the Latin granatus, meaning “the pomegranate” – an ancient fruit whose seeds resemble the crystals of the most common variety of garnet – the pyrope. For centuries garnet necklaces were worn by pharaohs of Egypt, a popular sarcophagus-stuffer for the afterlife. The term carbuncle was often used in ancient times to describe red garnets. Carbuncle was thought to be one of the four precious stones given to King Solomon by God.
- General composition: A3B2(SiO4)3, where Ca, Mg, Fe2+, or Mn2+ occupy the A site, and the B site contains Al, Fe3+, or Cr3+.
- Garnet Specific gravity: 3.4 – 4.3 (almandine 3.95-4.32, pyrope 3.53-3.87, spessartine 3.80-4.25, andradite 3.70-4.18, grossular 3.56-3.71 and uvarovite 3.40-3.90)
- Refractive index: 1.72-1.94 (almandine 1.75-1.83, pyrope 1.73-1.77, spessartine 1.79-1.81, andradite 1.86-1.94, grossular 1.72-1.80 and uvarovite 1.74-1.87)
- Garnet Birefringence: 0.000-0.005 (almandine 0.000, pyrope 0.000, spessartine 0.000-0.004, andradite 0.000-0.005, grossular 0.000-0.005 and uvarovite 0.000-0.005)
- Garnet Pleochroism: none
- Garnet Hardness: 6.5 – 7.5
- Garnet Luster: vitreous to resinous,
- Phenomena: chatoyancy due to minute asbestiform inclusions of pyroxene or amphibole, yielding a four-ray star when fashioned into a cabochon gem
- Garnet Transparency: transparent to opaque
- Garnet Cleavage: none
- Garnet Fracture: conchoidal, somewhat brittle
- Garnet Streak: white
- Hydrous garnets may contain up to 8.5% H2O
- Garnet Class: nesosilicates
- Garnet Crystal system: isometric; 4/m bar3 2/m
- Garnet Crystal habit: commonly forms as rhombic dodecahedrons, trapezohedrons, or a mixture of these two forms. Rarely as hexoctahedrons. Also as coarse or fine massive granular.
Pyralspite Garnet Group
- Almandine Garnet: Fe3Al2(SiO4)3
- Pyrope Garnet: Mg3Al2(SiO4)3
- Spessartine Garnet: Mn3Al2(SiO4)3
Ugrandite Garnet Group
- Andradite Garnet: Ca3Fe2(SiO4)3
- Grossular Garnet: Ca3Al2(SiO4)3
- Uvarovite Garnet: Ca3Cr2(SiO4)3
Less Common Garnet Species
- Calderite: Mn3Fe3+2(SiO4)3
- Goldmanite: Ca3V2(SiO4)3
- Hydrogrossular: Ca3Al2(SiO4)3-x(OH)4x
- Hibschite: Ca3Al2(SiO4)3-x(OH)4x (where x is between 0.2 and 1.5)
- Katoite: Ca3Al2(SiO4)3-x(OH)4x (where x is greater than 1.5)
- Kimzeyite: Ca3(Zr,Ti)2[(Si,Al,Fe3+)O4]3
- Knorringite: Mg3Cr2(SiO4)3
- Majorite: Mg3(Fe,Al,Si)2(SiO4)3
- Morimotoite: Ca3Ti4+Fe2+(SiO4)3
- Schorlomite: Ca3(Ti4+,Fe3+)2[(Si,Ti)O4]3
Olive-green to emerald-green rare and highly desirable gem variety of Andradite Garnet. The famous “horsetail” inclusion is often an identification mark that increases the stone’s value. Demantoids rival the fire of green diamonds because they have high dispersion. In fact, they were called “Green diamonds” in the past. A large demantoid was the focal point of a 1910 short novel by Alexander Kuprin” The Garnet Bracelet.”
Green to an emerald-green transparent variety of Grossular Garnet from Africa. It is very popular and commands high prices.
Orange to reddish-brown highly prized variety. Mandarin garnet, naturally occurring in a vivid orange color due to manganese in its composition. Mandarin usually originates from the African countries of Namibia and Mozambique. Tangerine Garnet is light orange to orange-yellow Spessartine Garnet, usually from Namibia and Mozambique.
Pale pink to violet-colored variety form of Garnet. Its light rose-red color is more purplish than typical garnets. It is usually an intermediary variety between Pyrope and Almandine, though more closely towards Pyrope in composition.
It exhibits a different color depending on the light source is a hybrid of the Pyrope and Spessartite that displays a color change from a light brownish, yellowish, or greenish in daylight to a pink or purplish color in incandescent light. A few rare specimens may even have a bluish color.
Light green to a light greenish-brown variety of Grossular Garnet.
Orange to an orange-brown, transparent variety of Grossular Garnet
Light pink, the transparent gem variety of Grossular Garnet.
Colorless, transparent variety of Grossular Garnet.
Garnet gemstone from the African country of Mali ranges in color from green to yellow to brown (though most often a greenish-yellow). The deposit of these Garnets was discovered in Mali in 1994, and this form of Garnet is a relatively new gemstone. The scientific classification of the Mali Garnets is not clearly identified; they can be either Grossular or Andradite, though they are usually an intermediary form closer in chemical structure to Grossular.
Colorless to black variety. Melanite is lustrous, opaque black or very dark red variety of Andradite Garnet.
Grossular Garnet with a light-mint-green color. Very refreshing. Also known as Merelani Mint Garnet, it is named for the region of Tanzania where it was first found. Merelani has a light bluish-green hue, unlike the rich green or yellowish-green hues of tsavorites and demantoids.
Malaia or Malaya garnet is a variety of light to dark slightly pinkish-orange, reddish-orange, and yellowish-orange mixture of pyrope, almandine, and spessartine with a little calcium.
Reddish-orange form of Spessartite Garnet (or, more accurately, a mixture intermediary between Spessartite and Pyrope) originates in the Umba River Valley in Tanzania and Kenya. On occasion, the term is used as a synonym for Spessartite.
Red Garnet from the African country of Mozambique, which produces fine quality Garnet gemstones. Mozambique Garnet is usually Almandine, but may also be Pyrope.
Raspberry-red variety of Grossular Garnet.
Form of Almandine Garnet exhibiting asterism in the form of a four-ray star.
Yellow to a brownish-yellow variety of Andradite Garnet.
Dark red to a violet-red variety of garnet.
White, yellow, yellow-green, brownish-red, orange, or black garnet.
Very common, inexpensive blood-red variety of garnet. Widely used in costume jewelry and Bohemian-style jewelry sold everywhere in Prague.
The rarest bright green garnet variety, so rare you can find it only in museum collections.
Garnet’s healing properties (insurance is not accepted): Garnet is a birthstone for January. Garnet is a 2nd Anniversary gemstone. Garnet represents love and commitment. It is said to revitalize feelings and enhances relationships by bringing warmth, devotion, understanding, trust, sincerity, and honesty. Said to control anger, although never scientifically tested.
The beryl family encompasses a group of very popular and precious gems. The single beryl species gave us charming Santa-Maria aquamarines and Colombian emeralds and tender pink morganites, heliodor in festive shades of yellow, ruby-red bixbites, and even colorless goshenites.
Emerald is typically heavily included; its inclusions can even help identify where it was mined. On the other hand, Aquamarines, morganites, and heliodors usually have fewer inclusions. Read about emeralds.
Aquamarine is a beautiful and plentiful gem of ancient lineage. It is a March birthstone. The name “aquamarine” means “blue water” in Latin.
The largest aquamarine ever found weighed 243 pounds. It was discovered in 1910 in Brazil. After cutting, it yielded over 200,000 carats. The Romans believed that a frog carved from aquamarine could reconcile enemies and make them friends.
They also thought it absorbs the spirit of love: “When blessed and worn, it joins in love, and does great things.”
The Greeks and the Romans believed an aquamarine could aid in a safe passage across the seas. Perhaps this is why they considered aquamarine the most appropriate gift in the morning after the marriage consummation. In Medieval times aquamarine was used to rekindle married couples’ love and render soldiers invincible. The same people believe that bathing will kill you.
Chrysoberyl was discovered in 1789. Cat’s-eye chrysoberyl, along with its non-phenomenal counterparts, is one of the most revered gems. Chrysoberyl and beryl are two completely different gemstones, although both contain beryllium. Additional confusion was caused by calling yellow-green chrysoberyl and completely unrelated mineral peridot by the same name – chrysolite. Chrysoberyl is a relatively hard natural gemstone measuring 8.5 on the Mohs scale close to the corundum’s 9. Two chrysoberyl varieties are the world’s most exotic and expensive gemstones: the Alexandrite and Cat’s-eye chrysoberyl.
Alexandrite is the color-change variety of chrysoberyl. Alexandrite is said to enable its wearer to foresee danger. Among celebrities who do not wear Alexandrite, we find Dr. Fauci. Alexandrite was first discovered in 1830 in Russia’s Ural Mountains and named after the young Czar Alexander II.
Cat’s eye chrysoberyl became popular in the late nineteenth century after British Prince Arthur presented his bride, Princess Louise Margarita, an engagement ring set with cat’s eye chrysoberyl. Instantly, the previously neglected variety of chrysoberyl became very fashionable.
Cat’s eye is an optical effect appearing as a concentrated band of light splitting stone in half. It is called chatoyancy, from the French “oeil de chat,” the appearance reminiscent of a feline eye. When chrysoberyl cabochon is lit up from above, half of the stone appears honey-colored, and the other half appears milky-white. This is called the “milk and honey” effect, and it’s a sign of the finest grade.
Topaz is durable, has a lot of fire and brilliance, and is very inexpensive. It looks equally good as a brilliant-cut – such as round, oval, cushion, or as a step-cut emerald. In nature, topaz comes in various colors, such as light gray, baby blue, light brown, taupe, or pale yellow.
The colorless topazes are nuked to induce the familiar bright-blue color. The irradiation results in a permanent color and leaves no radioactive residue.
Deep pink or red variety called Precious topaz or Imperial topaz is costly.
Due to its excellent hardness (8 on Mohs scale), spinel works exceptionally well as a diamond substitute. A spinel's girdle can be left exposed without worrying that it will get chipped immediately. Spinel works well in five- or three-stone engagement rings, as well as solitaires.
Precious red spinels have long been mistaken for rubies. For example, the Black Prince's ruby mounted in front of the British Imperial State Crown turned out to be red spinel.
Recently spinel became August's second birthstone. Thanks to its array of colors ranging from red, orange, pink, purple, and lavender to black, spinel is a jewelry designer's dream.
The world's largest faceted peridot weighs 311 carats and is on display at the Smithsonian. This cushion-shaped originated from the Red sea island Zabargad, Egypt, where peridots were mined as early as 1500 B.C. by the Jewish slaves of Pharaohs.
Peridots were favorite stones of King Edward VII of England who gave the name to the Edwardian jewelry period.
December birthstone dubbed "a poor man's sapphire," Tanzanite is marketed as a sapphire substitute, but it is usually too purple to pass as a sapphire. The purplish-blue gemstone named Tanzanite by Henry Platt, the president of Tiffany & Co., in 1968, is found in only one location in Africa, near Mount Kilimanjaro. Given its scarcity, it sells at a high premium.
Virtually all tanzanite occurs in nature as opaque white pebbles and needs to be heat-treated to turn blue and become transparent. Tanzanite's trippy property called trichroism causes the stone to look blue, violet, or burgundy depending on where it is facing.
Tanzanite is the most popular variety in the Zoisite mineral family. Zoisite is translucent or transparent and has a vitreous luster. Its varieties can be brown, grey, yellow, blue, violet, green, pink, and colorless. Zoisite is a relatively hard gem, measuring 6.5 to 7 on the Mohs scale, but prone to breaking due to its perfect cleavage.
Natural zircon is a greatly underrated gemstone, in part because it was a very popular diamond simulant in the early 1900s. Cubic zirconia, colorless moissanite, and lab-grown diamonds are better substitutes, rendering zircon useless as a fake diamond. However, the name zircon still carries the stigma associated with its checkered past.
Zircons are double-refractive. They show a degree of birefringence, which is doubling-up of facets which makes it easy to distinguish them from single-refractive
gems like diamonds. Although birefringence may detract from brilliance, it is an unusual optical feature that should be appreciated for its uniqueness.
Zircon is relatively hard (7.5 on Mohs scale) and has exceptional fire due to its strong dispersion. Colorless zircon is known for its brilliance and fire. Zircon’s high specific gravity always stands out among other similar looking gems.
Natural zircon is known for its distinctive beauty and occurrence in a broad range of colors. It can be blue, green, colorless, grey, brown, red, orange, or yellow.
Zircon naturally comes in several colors; blue is the most popular variety due to its vivid vibrance. The blue zircon is not only outstanding and comparable to the natural blue in diamonds and aquamarines, but it is also much more affordable. The darling of the Victorian era, the blue zircon remains the most popular color even now. The most desirable electric-blue zircons are heat-treated brown crystals found mainly in Cambodia.
Yellow is the most iconic color of zircons. Until diamond deposits in Africa yielded plenty of colorless diamonds, the pale yellow zircons were used to fool unsuspecting buyers into thinking they were getting a Brazilian diamond. Although the most popular color is blue, the canary yellow and honey colors are gorgeous, and they are an important yellow gemstone on the jewelry palette.
An unusual property called thermochromism occurs when some yellow zircons from Kaduna, Nigeria, and Singida, Tanzania, cycle from brown to vivid orange when gently heated. Heating it with a cigarette lighter for about 20 seconds will do the trick. Once zircon cools down, the process can be repeated.
Red zircons occasionally have a curious physical property called tenebrescence – quickly turning dark-brown or even black when exposed to sunlight after being kept in the dark. Once zircon gets too hot, it will turn colorless, and all the tenebrescent and thermochroic properties will be lost.
The rarest zircon color variety is green, sometimes called beccarite. Green zircons are usually olive-green, similar to peridots.
Taaffeite, or pink zircon, was first discovered in 1945 by Dublin gemologist Richard Taaffe who found at the local jeweler what he initially thought was a pale mauve spinel. The double-refractive gem was identified as a new zircon species upon further testing. Not until four years later, another taaffeite was found in a parcel of Sri Lanka gems.
Kunzite is a variety of the mineral spodumene. It’s named after gemologist George Frederick Kunz. Hurry up before Elon Mask snaps all Kunzite from the market because the pegmatites that yield the pink gem are a source of lithium for electric batteries.
- Chemical Composition: LiAlSi2O6
- Hardness: 6.5-7
- Crystal System: Monoclinic
- Refractive Index: 1.66-1.68
- Specific Gravity: 3.1-3.2
- Double Refraction: .015
- Luster: Vitreous
- Cleavage: 1, 2 - prismatic
- Mineral Class: Spodumene
Moonstones have mysterious billowing light deep inside the stone caused by scattered light passing through the exsolution lamellae. Clear moonstone with a blue sheen, the most valuable kind, rarely exceeds 15 carats in size.
Those who do not love moonstones are patently bad people, like Inez, the protagonist's fiancee, and her condescending, obnoxious, and close-minded parents in Woody Allen's "Midnight in Paris."
Moonstones are prized for their adularescence — a billowy, moonlight-like sheen. The transparent and colorless moonstones with blue adularescence are the most valuable, while ranslucent cabs with red and yellow adularescence, so-called rainbow moonstones, are common and inexpensive.
Moonstones are usually cut in a smooth-domed cabochon shape to maximize the adularescence effect and minimize damage from scratches. Moonstone carvings are typically made from cheaper, translucent material.
The fine moonstones mined in Sri Lanka, and Southern India are quite rare. The rainbow variety is found in India and Madagascar.
The pearls are gems grown within the soft tissue of an oyster around a microscopic irritant such as a grain of sand that found its way inside the shell. There are two types of pearls identical in composition and appearance and different only in how they were conceived – natural and cultured.
Natural pearls are seeded naturally, while cultured pearls are acquired through farming and harvesting processes where the mollusk is seeded by humans. In both cases, the mollusk coats the irritant with layers of inorganic deposits called nacre, creating a pearl. Natural pearls are scarce and expensive. The vast majority of the pearls available on the market today are cultured.
Nacre is the material of which pearls are composed; it consists of aragonite – calcium carbonate, and conchiolin, a complex protein forming mollusk shells. It is strong, resilient, and iridescent.
The highest quality Akoya pearls originating from Japan are called Hanadama Akoya, “flower pearls” in Japanese. Akoya pearls have highly desirable white, grey, cream, and blue body color with silver, pink and green overtones ranging from two to ten millimeters. They are commonly perfectly round in shape, although irregular-shaped Akoya pearls can also be found.
South Sea pearls are the most sought-after variety of pearls, often called the Queen of Pearls. The high failure rate during the cultivation process makes South Sea pearls one of the most valuable on the market. The perfectly spherical specimens without dents and blemishes are rare and command very high prices.
The Melo sea snail makes the orange-hued pearl prized for its flame-like appearance.
Conch are exceptionally rare pink pearls made of a porcelaneous (non-nacreous) material.
- Wrinkles result from uneven growth of the nacre due to odd-shaped seeds
- Spots are slight color variations
- Abrasions are scratches or scuffs that impact the luster of the pearl.
- Dents, divots, and pits are various indentations in the nacre.
- Mottling and bulleting is a pattern on the surface created inside the oyster. It can be desirable because it indicates a thick layer of nacre.
- Kobs and tips are growth marks.
- Circles are a growth pattern that imparts a unique look and is not considered a blemish.
Natural Golden South Sea pearls ranging from pale champagne to rich 24-karat gold color come from the tropical lagoons of Australia, Indonesia, and the Philippines. They are produced by the “gold-lip” South Sea oyster and are valued for their warm, regal tones. Sometimes white pearls are dyed to imitate the naturally occurring golden color. The dyed pearls are less valuable.
There are several different systems for pearl rating. The characteristics affecting pearl’s grade are:
- Luster: Bright, highly reflective pearls get the higher rating
- Blemishes: They are evaluated by size, type, number, and location
- Nacre thickness: The thicker the nacre, the higher the value
- Color: White and grey-white are the most valuable
- Size: Larger is typically more valuable
- Shape: Roundness and symmetry are prized
- Match: a uniform arrangement in a string of shape, color, luster, spotting, and graduation.
THE AAA-A SYSTEM
This grading system ranks pearls from AAA to A, with AAA being the highest.
- AAA: Nearly flawless pearls with a high luster and a surface that’s 95 percent free of defects
- AA: High luster with a surface that’s 75 percent free of defects
- A: Lower luster and defects on more than 25 percent of the surface.
THE A-D SYSTEM, OR TAHITIAN SYSTEM
The A is the highest grade, and the D is the lowest. The A-D system is based on a French Polynesian government standard.
- A: Very high luster, and only 10% of the surface or less has defects
- B: High to medium luster and less than 30% or less of the surface is defective
- C: Medium luster and 60% of the surface or less is defective
- D: The lowest rating. Luster is not evaluated; only surface defects are.
Saltwater pearls come in three main varieties. They generally have a better quality than freshwater pearls, reflected in their higher demand and price. The most common varieties include Akoya, South Sea, and Tahitian pearls. Before the Japanese started cultivating Akoya in the early 20th century, pearls were rare and expensive. Today Akoya is the most abundant variety of saltwater pearls.
With their perfectly spherical shape and high luster, Akoya pearls are formed by small Pinctada fucata oysters, also known as Akoya oysters. They come from waters surrounding Japan, China, Korea, and Vietnam. Each oyster can produce only one or two pearls at a time, and the limited production increases their value.
South Sea pearls are the most sought-after variety of pearl types cultivated in Australia, the Philippines, Myanmar, and Indonesia. They grow inside the Pinctada maxima oysters, which are the largest pearl oysters in the world. The South Sea pearl color palette consists of white and golden hues, with pink, green, and blue overtones. South Sea pearls can grow up to 22 millimeters in diameter and are highly prized for their satin-like luster, elegant appearance, and size.
Tahitian pearls come exclusively from Tahiti and other French Polynesian islands and are the most sought-after naturally dark gems. They are produced by the black-lipped Pinctada margaritifera oyster, which doesn’t live anywhere else. Tahitian pearls occur in black, dark grey, charcoal, peacock green, and aubergine colors with silver, lavender, and blue overtones. They can grow as large as 21 millimeters. However, less than 10% of the harvest qualify for export because, according to the internationally accepted quality standards, a true Tahitian pearl should have a nacre at least 0.8-millimeter thick. Tahitian pearls were once coveted by Queen Elizabeth I.
Jade is revered in China for over 4000 years. The most valuable jade is the Imperial Jade, emerald-green semi-transparent to translucent jadeite colored by chromium. It is mined in northern Myanmar at the Hpakan-Tawmaw jade tract in Kachin province.
Jadeite and nephrite can look similar, and both are often called jade, but they have a different chemical composition, crystal structure, and hardness. The Chinese jade is actually nephrite because the rarer and more valuable Jadeite is found in Burma and hasn't found its way to China until about 300 years ago.
Type A Jadeite
Completely natural and without any treatment. A colorless wax may be used for polishing the surface. It is the most valuable and rarest type of jadeite.
Type B Jadeite
Bleached to improve the color and fade brown hues and impregnated with polymers to add strength and improve clarity and transparency.
Type C Jadeite
Dyed to improve its color consistency. This jade is usually heated to absorb the dye.
Bleached, impregnated with polymers or dyed material.