1.5ct Oval Orange-Pink Topaz GIA Certified
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Regular cleaning is essential to maintain the brilliance of your emerald jewelry. However, it's crucial to use gentle cleaning methods to avoid any harm. Prepare a mixture of lukewarm water and a mild, phosphate-free soap or detergent. Soak your emerald jewelry in this solution for a few minutes and then gently scrub with a soft brush, such as a toothbrush with soft bristles. Be sure to reach all the nooks and crevices. Rinse the jewelry thoroughly with clean water and pat it dry with a soft, lint-free cloth.
0.6ct Oval Green Emerald Stud Earrings set in 14k Yellow Gold
Proper care and handling is crucial for preserving the beauty and longevity of your emerald jewelry. By following these guidelines, you can ensure that your emeralds continue to shine brilliantly and remain cherished heirlooms for years to come. Remember to store them carefully, avoid exposure to harsh chemicals and high temperatures, clean them gently, and seek professional maintenance when necessary. With attentive care, your emerald jewelry will continue to captivate with its timeless elegance and allure.
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While diamonds are timeless and classic, they are also incredibly common. Coloured gemstones, on the other hand, offer a wide range of unique colours and hues that can help you express your individuality and personality. Whether you prefer the deep green of an emerald, the rich red of a ruby, the classic blue of a sapphire, or the fiery sparkle of a spinel, there is a gemstone out there that is perfect for you and your partner
1.04ct Red Spinel & Diamond Ring set in 18k White and Yellow Gold
In addition to their beauty and uniqueness, coloured gemstones also hold significant symbolism and meaning. For example, emeralds have long been associated with love and fertility, making them an excellent choice for an engagement ring. Rubies, on the other hand, are often associated with passion and romance, while sapphires are thought to represent loyalty and trust. By choosing a coloured gemstone for your engagement ring, you can add a deeper layer of significance to both your jewellery and your relationship.
Another advantage of coloured gemstones is their durability and rarity. While diamonds are known for their hardness, many coloured gemstones are equally as durable, if not more so. For example, sapphires rank just below diamonds in terms of hardness, but have no cleavage making them an excellent choice for an engagement ring that will be worn every day. Additionally, coloured gemstones such as emeralds and spinels are much rarer than diamonds, making them an excellent choice for those who want something truly unique and special.
1.59ct Colombian Emerald Diamond Ring set in 18k Yellow Gold, GIA Certified
Whether you're looking for a stunning emerald three stone engagement ring, a romantic ruby ring, or a classic sapphire halo engagement ring, skyjems.ca has something for everyone.
Egypt was eventually conquered by the Ottoman Empire in 1517, after which peridot gems began to appear in Ottoman jewellery. Most famously, the gilded walnut throne known as the “Bayram Tahti” (English: “The Gold Festival Throne”) was adorned with over 950 peridot gemstones and given to sultan Murad III in 1585. Despite the emergence of peridot jewels among Ottoman treasures, there are still no definitive descriptions of Zabargad in the Empire's scholarly texts, implying that the Ottomans were not mining period on the island and that that these gems may have come from stored wealth found in Constantinople, Alexandria, and/or Cairo, although this is not entirely clear. It is possible that academics of the time were merely unaware of Zabargad and its peridot as the Island is briefly referenced with the corrupted name “Zomorgete” in the logbook of Portuguese explorer João de Castro after he sailed through the Red Sea in 1541 under guidance of local navigators, suggesting that nearby populations knew of Zabargad even if it was not being actively mined or documented by governing powers.
After the 16th Century C.E., the history of Zabargad continued to be muddled; the next time that written information about the Island surfaced, it was still not clear how much was known about the stones found there. In 1769 the island was supposedly visited by Scottish traveller James Bruce of Kinnaird who wrote that he found green crystal fragments there known in Egypt as “siberget”, a local name for emerald, but that these stones were much too soft to have been genuine emeralds; despite an obvious similarity between Bruce’s account and the peridot of Zabargad, it is curious that the placement of the island which Bruce had provided in his writings does not perfectly match the geographic location of Zabargad. James Raymond Wellsted, a lieutenant in the Indian Navy, is said to have visited Zabargad during his time travelling the Red Sea in the early 19th Century C.E.. Wellsted wrote of the island using many names including “St. John’s Island”, “Bruce’s Island”, “Siberget”, and “Zumrud”; calling the Island by the name “St. John” has been erroneously attributed to Crusaders of the middle ages even though Wellsted is generally regarded as the source for this name, and interestingly the latter two names are both references to emerald, reflections of the continued confusion in distinguishing between the verdant beryl and peridot. In his writings Wellsted mentions the green gems found on Zabargad and describes the remnants of mining sites; he drew a connection between the stones he encountered and the green stones Pliny the Elder referred to as “smaragdus”, despite that they were actually the “topazos” stones which Pliny had attributed to the island.
It was only in 1906, after a push from the Turkish viceroy residing in Egypt, that full scale mining began again on the island of Zabargad. These operations continued until 1922 when the mining lease was acquired by the Red Sea Mining Company, who then worked the peridot mines of Zabargad for over a decade before abandoning their operations at the start of World War II. Large quantities of peridot were unearthed during this time period, and most peridot gemstones seen in Art Deco jewellery of the early 20th Century were sourced directly from Zabargad. Eventually the Island was reclaimed by the Egyptian government in 1958 under the leadership of President G. A. Nasser, but the island’s deposits had already run low and little mining activity has taken place since. In 1986, the island was given official ecological protection and has more recently become part of Egypt’s Elba National Park.
The island of Zabargad itself is now known to reside about 96.5 kilometres (60 miles) to the southwest of the Ras Banas Peninsula. A small and rather inhospitable island, the biosphere on Zabargad is limited to turtles shrubs and a few species of bird, and its shores are surrounded with some of the largest coral reefs found in any inland sea; there are no freshwater sources found on the island, a limitation that would have contributed to the logistical difficulty of mining peridot from its slopes. Part of the global rift system, Zabargad would have arisen out of volcanic activity associated with the East African Rift Valley; the magmatic activity and metamorphism which lead to the birth of Zabargad would have been an ideal precursor for the formation of the peridotites which are found in numerous places across the island. The highest point on the island, which rises about 235 metres above sea level, now known as “Peridot Hill”, the eastern slopes of which were once home to some of the largest and highest quality olivine formations found on Zabargad. About 150 mining pits have been identified on the island, with some ceramics found near them dating to about 250 B.C.E.. Most of the crystals found on Zabargad were located somewhat close to the surface and had weathered out from their host rock, making extraction of the gem materials relatively easy by contemporary standards.
With its legendary history and beautiful characteristics, peridot has certainly acquired a timeless appeal that sets it apart from many of the gemstones commonly used in bespoke jewellery pieces. A stone with class and charisma, peridot should never be overlooked or forgotten when exploring the realm of natural green gems. Peridot is truly among the classic gems of humankind and will continue to play a key part in practice of expressing creativity through jewellery and design.
© Yaĝé Enigmus
]]>Jewelry can be classified into various types based on different criteria such as the materials used, the intended use, and the design. Some common types of jewelry are:
Fine Jewelry: Fine jewelry refers to high-quality, luxury pieces made with precious metals such as gold, silver, and platinum and often adorned with precious gemstones such as diamonds, sapphires, and rubies.
Costume Jewelry: Costume jewelry, also known as fashion jewelry, is made with non-precious materials such as glass, plastic, and base metals and is intended to complement an outfit or fashion statement.
Bridal Jewelry: Bridal jewelry is designed for brides to wear on their wedding day and includes pieces such as necklaces, earrings, bracelets, and tiaras.
Men's Jewelry: Men's jewelry includes pieces specifically designed for men, such as cufflinks, tie bars, and watches.
Children's Jewelry: Children's jewelry is designed for children and includes pieces such as bracelets, necklaces, and earrings.
Jewelry can be made from a wide range of materials, including precious and semi-precious stones, metals, and organic materials. Here are some of the most commonly used materials in jewelry:
Precious Metals: Precious metals include gold, silver, and platinum. Gold is the most popular metal used in jewelry and is available in a range of colors, including yellow, white, and rose. Silver is less expensive than gold and is commonly used in costume jewelry. Platinum is a rare and valuable metal that is popular for engagement rings and other fine jewelry.
Gemstones: Gemstones are a popular choice for jewelry, and there are countless types of gemstones available, including diamonds, rubies, sapphires, emeralds, and more. The value and rarity of a gemstone depend on its quality, size, and color.
Organic Materials: Organic materials used in jewelry include materials such as pearls, coral, and ivory. Pearls are a popular choice for bridal jewelry and are available in a range of colors and sizes.
Non-Precious Metals: Non-precious metals used in jewelry include materials such as brass, copper, and stainless steel. These materials are commonly used in costume jewelry and can be plated with precious metals to create a more expensive look.
Jewelry nomenclature is the terminology used to describe different aspects of a piece of jewelry. Here are some of the most common terms used in jewelry nomenclature:
Setting: The setting is the part of a piece of jewelry that holds the gemstone in place. Settings can be made from various materials such as metal, and they can be designed in a variety of styles, including prong, bezel, and channel settings.
Clasp: The clasp is the mechanism that is used to fasten a piece of jewelry, such as a necklace or bracelet. Clasps can be made from various materials such as metal and can be designed in a variety of styles, including lobster and toggle clasps.
Karat (K): Karat is a unit used to measure the purity of gold. 24 karat gold is pure gold, while 18 karat gold is 75% gold and 25% other metals.
Carat: Carat is a unit used to measure the weight of a gemstone. One carat is equal to 0.2 grams, and the price of a gemstone increases exponentially with its carat weight.
Hallmark: A hallmark is a mark stamped on a piece of jewelry to indicate the metal's purity and the manufacturer's or jeweler's identity.
Cut: The cut refers to the way a gemstone has been shaped and faceted. The cut affects the gemstone's brilliance and fire, and different types of cuts include round, oval, pear, and princess cuts.
Color: The color of a gemstone can vary widely depending on the type of stone. For example, diamonds can be found in various colors, including white, yellow, pink, and blue. The color of a gemstone is one of the factors that determine its value.
Clarity: The clarity of a gemstone refers to the presence or absence of inclusions, or internal flaws, in the stone. The fewer inclusions a gemstone has, the more valuable it is.
Design: The design of a piece of jewelry refers to its overall aesthetic, including its shape, size, and style. Different types of jewelry designs include classic, modern, and vintage.
Setting Style: The setting style of a piece of jewelry refers to the way the gemstone is held in place. Different setting styles include prong, bezel, and channel settings.
Fineness: Fineness is a unit used to measure the purity of silver. Pure silver has a fineness of 999, while sterling silver has a fineness of 925.
Alloy: An alloy is a mixture of two or more metals. In jewelry, alloys are often used to make metals more durable and resistant to corrosion. For example, 14-karat gold is an alloy of 58.5% gold and
Hallmark: A hallmark is a mark stamped on a piece of jewelry to indicate the metal's purity and the manufacturer's or jeweler's identity.
Enamel: Enamel is a type of decorative coating that is often applied to jewelry. It is made from powdered glass and is melted onto the surface of the metal to create a smooth, colorful finish.
Filigree: Filigree is a decorative technique in which thin wires or threads of metal are twisted and soldered together to create intricate patterns.
Casting: Casting is a method of creating jewelry by pouring molten metal into a mold. This process is often used to create complex or intricate designs.
Soldering: Soldering is a technique used to join two or more pieces of metal together using a metal alloy called solder. This process is often used in jewelry making to attach components, such as clasps or settings, to the main piece of jewelry.
Beading: Beading is a technique used to create jewelry using small beads. Beads can be made from various materials, including glass, wood, and gemstones.
Wirework: Wirework is a technique used to create jewelry using thin wires of metal. The wires are twisted and shaped to create intricate designs and patterns.
Lapidary: Lapidary is the art of cutting, shaping, and polishing gemstones. It requires a high level of skill and precision and is often used in jewelry making to create custom-cut gemstones.
Repousse: Repousse is a technique used to create a raised design on a piece of metal by hammering it from the back. This process is often used in jewelry making to create detailed designs and patterns.
Earrings: Earrings are pieces of jewelry that are worn on the ear. They can be made of various materials, including gold, silver, and gemstones.
Necklace: Necklaces are pieces of jewelry that are worn around the neck. They can be made of various materials, including pearls, beads, and gemstones.
Bracelet: Bracelets are pieces of jewelry that are worn on the wrist. They can be made of various materials, including metals, leather, and gemstones.
Ring: Rings are pieces of jewelry that are worn on the finger. They can be made of various materials, including gold, silver, and gemstones.
Art Deco: Art Deco is a style of design that originated in the 1920s and 1930s. It is characterized by geometric shapes, bold colors, and streamlined forms.
Retro: Retro refers to a style of design that originated in the 1940s and 1950s. It is characterized by curves, bold colors, and feminine forms.
Minimalist: Minimalist refers to a style of design that is characterized by simplicity and restraint. Minimalist jewelry is often sleek and understated, with clean lines and minimal ornamentation.
Vintage: Vintage refers to jewelry that is at least 20 years old. Vintage jewelry can be from any era, and it is often highly valued for its uniqueness and historical significance.
Contemporary: Contemporary jewelry refers to jewelry that is currently being designed and produced. It often incorporates new materials and techniques and is inspired by current trends and styles.
Pliers: Pliers are a tool used in jewelry-making to bend and shape wire and metal.
Files: Files are used to smooth and shape metal in jewelry-making.
Soldering torch: A soldering torch is used to heat and melt metal when soldering pieces of jewelry together.
Mandrel: A mandrel is a tool used to shape and size rings.
Loupe: A loupe is a small magnifying glass used to examine gemstones and other small details in jewelry.]]>Tanzanite is a gem variety of the mineral zoisite. It is notable for its striking pleochroism, which is a change in a gem’s color depending on the angle at which it is viewed. Pleochroism is a phenomenon not commonly seen in most gems, and the uniquely vibrant display that we observe in Tanzanite is truly unlike any other stone.
Tanzanite crystal exhibiting pleochroism; Image by Michael C. Roarke via Mindat
The vast majority of Tanzanites on the today’s market are heated to enhance their color. While some stones such as sapphires are subjected to temperatures up to 2000°C, Tanzanite is treated in gentler conditions ranging from 500 to 800°C. This treatment allows trace amounts of vanadium within the stones molecular structure to change into a state that produces a range of striking violet-blue hues.
A 16.57ct faceted Tanzanite before and after heat treatment next to the rough it was cut from; Image by Orasa Weldon via GIA
2.44ct Heat treated Tanzanite; Image by Skyjems
As its name suggests, this gem originates from only one deposit in Tanzania. The area of mining measures only 20 square kilometers, and experts estimate that the source will be completely depleted within the next 10 to 12 years. This limited availability of Tanzanite makes high quality stones extremely rare and difficult to find in most retail settings.
Another factor of Tanzanite’s allure is its high refractive index (RI). Refractive index describes a gem’s ability to bend and alter light. Stones with higher RIs are capable of taking on a higher polish and exhibit excellent brilliance. With an RI of 1.7, Tanzanite is an unquestionably good contender for jewelry with exceptional bling factor. For comparison, the RI of sapphire is 1.76.
Exceptional brilliance is demonstrated in this 2.83ct cushion cut Tanzanite; Image by Skyjems
Since Tanzanite has a slightly lower hardness than some other stones, special care is required when designing and creating jewelry with it. Here at Skyjems, we have the experience and attention to detail required to bring your ideas to life! Here are some examples of designs featuring Tanzanite that we have made in the past.
3.08ct Tanzanite and White Sapphire Ring set in 14K Rose Gold
Tanzanite and White Sapphire Ring in 10K White Gold
Tanzanite Earrings in 14K White Gold
Tanzanite and Diamond Pendant in 14K Yellow Gold
Tanzanite is a truly under-utilized gem in the world of jewelry. Ready to create a one-of-a-kind piece with this show-stopping stone? Let us help you create the jewelry of your dreams! Contact us today to get started.
]]>The cratered summit of Mount Vesuvius; Image: Italy Magazine
`Large numbers of naturally occuring blue zircon crystals have been discovered within the syenite nodules from the Avellino eruption, with these stones receiving some of their most recent scientific evaluations in 2021. These blue zircons were found to contain the same trace elements found in zircon crystals from Cambodia’s Ratanakiri province, including uranium (U), thorium (Th), hafnium (Hf), niobium (Nb), and rare earth elements like cerium (Ce) and neodymium (Nd), however the density of mineral inclusions in these stones is considerably higher than that of gem grade zircon crystals from southeast Asia. Interestingly, crystal zones which contained more densely packed inclusions appeared yellowish or brownish in transmitted light as opposed to the colourless appearance observed in other crystal zones; conversely, treated blue zircons from Cambodia appear light blue when viewed in transmitted light. In addition to the analysis of unaltered crystals, some of the Vesuvian blue zircons were also examined after receiving the same heat treatments that most commercial blue zircons are subjected to.
Blue zircon crystals on matrix from the San Vito Quarry on the western slopes of the Somma-Vesuvius Complex in Campania, Italy; Image: Mindat/ Lugi Chiappino
When heated under the same oxygenless conditions that produce the blue hues seen in heated zircon gemstones from Cambodia, the colour of blue zircon crystals from Mount Vesuvius did not intensify, however these stones did display yellowish tones after being heated in the presence of oxygen much like some heated zircons from southeast Asia; the yellow colour seen in the treated Italian material was most intense in crystal zones which contained higher concentrations of mineral inclusions. This could imply a degree of similar chemistry between the zircon crystals of Mount Vesuvius and some zircon crystals from southeast Asia. Following heat treatment, the Italian blue zircons were exposed to long wave ultraviolet light (LWUV) to test their tenebrescence and compare it with the tenebrescent shift that has been observed in some treated blue zircons from Asia; ultraviolet light exposure had no discernible effect on the colour of blue zircon crystals recovered from Mount Vesuvius, whereas LWUV can temporarily changed the colour of some treated blue zircons from Asia to a brownish hue.
Zircon crystals from Mount Vesuvius subjected to heat treatment under oxidising/reducing conditions and a treatment naive crystal viewed in reflected light (RL) and plane polarised light (PPL); Image: Sun et. al.
Similarities in chemistry and heat treatment results suggest that its plausible the colour of italian blue zircons and Asian blue zircons could be derived from the same source; earlier investigations suggest that the stones found in Italy were heated after formation by proximal magmatic activity, a possible explanation for the anecdotal reports of untreated blue zircon crystals in other locations as well. Differences in inclusion profiles, tenebrescence, and behaviour in transmitted light do however point to a different explanation for how the Vesuvian zircons got their colour; it has been more recently proposed that the blue colour seen in zircon crystals from the Avellino eruption is not caused by any sort of chromophore but is instead the result of light scattering, most likely Raleigh type light scattering, as blue zones of the Italian zircons only appeared blue when given oblique illumination rather than perpendicular transmitted light; light scattering is the same phenomenon that causes the sky to appear blue, and it is caused by the presence of finely dispersed dust particles in the air. In a manner similar to how dust in the atmosphere causes light scattering, the scattering of light in Vesuvian zircons is thought to occur because of the highly refractive inclusions that have been found dispersed throughout the stones.
A faceted blue zircon gemstone from Cambodia; Image: Skyjems
One of the Earth’s most underrated treasures, zircon gems are a fantastic addition to countless bespoke jewellery designs and almost any gemstone collection. Quintessential parts of the planet, zircon crystals are as important to science as they are beautiful. These mysteriously colourful stones continue to enliven the world with their brilliance, and should never be neglected or forgotten.
© Yaĝé Enigmus
]]>A collection of faceted blue zircon gemstones from Cambodia; Image: GIA/ Robert Weldon
The majority of blue zircon gemstones currently available in the jewellery marketplace, and nearly all Cambodian blue zircons, originate from the Ratanakiri Province of Cambodia in the northeastern portion of the country, a region where extensive gem mining takes place; aptly so, the name “ratanakiri” is derived from the Khmer words for “gem” and “mountain”, giving the possible english interpretations of either “mountain of gems” or “the place of gems and mountains”. Blue zircon gemstones have been popular since the Victorian era, but larger scale mining of zircon in Ratanakiri Province did not begin until the 1930’s, with some of the more productive deposits being located in the area of Ratanakiri Province’s capital, Ban Lung, and the nearby settlement of Bae Srak, as well as the area surrounding Bo Keo about 25 kilometres east of the capital. Multiple zircon mines in Ratanakiri Province produce brown zircons which turn blue upon heating, but the mines of Bae Srak specifically are associated with blue zircons of the richest colour, while stones from other Cambodian sources tend to exhibit lighter blue hues after treatment; no naturally blue crystals have ever been reported from the mining operations of Bae Srak.
A map of Cambodia showing Ratanakiri Province outlined in red; Image: Zeug et. al.
Geologically, Ratanakiri Province is part of the Indochina Cratonic Terrane formation, which stretches across southeast Asia and covers parts of Cambodia, Thailand, Myanmar, and Vietnam; due to similar geologic conditions in these countries, zircon deposits which produce brown stones amenable to the induction of blue colour by heat treatment have been found in multiple locations outside of Cambodia. Blue zircons have been successfully produced from brown stones of found in the Bang Kacha and Tok Prom areas of Thailand’s Chanthaburi Province, and the Bo Phloi area of Thailand’s Kanchanaburi Province, as well as from brown stones mined in the Central Highlands of Vietnam and Myanmar’s Shan State. In 2021, a new deposit of brown zircons was discovered near Maripa in the Chikwawa District of southern Malawi, with some of the stones from this find exhibiting a blue colour after heat treatment, although very little gem material has been produced from this deposit to date. Interestingly, some green metamict zircon gems from Sri Lanka may also turn light blue when subjected to heat treatment. Even though sources for blue zircon are found in numerous locations, Cambodia’s Ratanakiri Province remains the largest single source for this zircon variety.
A faceted blue zircon gemstone from Cambodia; Image: Skyjems
The treatment process for blue zircon involves heating stones for a few hours in the absence of oxygen to temperatures of approximately 900-1000°C, a heat level low enough to be achieved with charcoal fires; typically carbon monoxide and/or nitrogen gas are used to produce oxygenless conditions within the crucibles which hold stones during the course of treatment. In some cases, brown stones may turn colourless when heated. Curiously, the blue colour of treated zircon gemstones is not apparent immediately after ideal treatment temperatures are reached, and hot stones will initially show white or silvery tones; only after being allowed to cool do freshly treated zircon stones of the right chemistry reveal their attractive blue hues. What is also interesting about these treated stones is that some have been reported to temporarily change colour in response to light exposure, a phenomenon known as “tenebrescence”; exposure to long wave ultraviolet light can cause tenebrescent blue zircons to become brownish in colour for some time before eventually returning to their original blue hues. Blue zircon would be substantially less available for use in gemstone jewellery without the application of heat treatments, as blue is the rarest colour to occur naturally in this mineral without human intervention, followed by green and then red. There have been anecdotal reports from Vietnam, Cambodia, Myanmar, and Sri Lanka of untreated blue zircon crystals surfacing as part of raw material yields primarily composed of other zircon colours, however these accounts are so few in number that they are not regarded as particularly significant in the context of the gem trade, and never have these stones been discovered as part of a full “deposit” of blue zircon; the only place where a high enough concentration of untreated blue zircon has been found for the locality to be regarded as the site of a naturally blue zircon deposit is in Campania, Italy among the syenites which were once ejected by the volcanic activity of Mount Vesuvius.
Heated blue zircon crystals (left) and gemstones (centre) from Malawi, with crystals of their untreated source material (right); Image: Gemological Institute of America
© Yaĝé Enigmus
]]>A 250µm zircon crystal viewed under high magnification; Image: Wikipedia
The uranium content of zircon crystals also makes them good candidates for fission-track radiometric dating. Certain radioactive isotopes of uranium, like uranium-238, will undergo nuclear fission during as part of their radioactive decay, often releasing gamma radiation in the process which then has the potential to damage or disrupt the integrity of materials in its immediate path, leaving a trail or “ion track” of damage in its wake; the concentration of ion tracks in a given material can be used to determine the number of fission events which have taken place since its formation, and referencing this value against the halflife of uranium-238 then indicates the material’s age. Using zircon crystals to radiometrically date materials is an important part of current geological research, augmenting investigations into the formation of igneous rocks, the origins of sediments, the movement of mountain belts, and the age of undated rock layers or “strata”. Radiometric dating of zircon crystals is also sometimes utilised in archaeological research to determine the age of some rock-bearing artefacts.
Ion tracks in a mineral sample made visible by chemical etching; Image: Wikipedia
Zircon’s ability to resist weathering and high temperatures allows zircon crystals to survive in the Earth’s crust for much longer periods of time than virtually any other mineral. Because of this, there exist certain zircon crystals which are regarded as the oldest crystallised mineral formations on planet Earth; zircon crystals from the Narryer Gneiss Terrane in Western Australia, part of the Yilgarn Craton rock formation, have been dated to over 4.4 billion years ago based on the results of uranium-lead dating, making these crystals older than any other dated mineral formation and nearly as old as the Earth itself. Due to the longevity of zircon crystals, many samples are not only present during intense geological shifts but they also frequently survive them; this in combination with the slow continuous crystal growth which occurs for many zircon crystals after their initial formation allows some older crystals to be used as records of the geological changes that they were subjected to, thus providing insight into the early history of planet Earth. Individual stages of crystallisation will carry traces of what the environmental conditions surrounding a crystal were like during that stage of growth, freezing a snapshot of those conditions in time within a crystal, much like a stony time capsule. The layers of a zircon crystal can then be interpreted in a manner reminiscent of how one may read the rings of a tree trunk, revealing information about the geology of a given period during the crystal’s time in the Earth’s crust. Multiple variables within the structure of zircon can provide different pieces of information about the environment in which it grew, such as which impurities are present, the concentration of impurities, the integrity of zircon’s crystal lattice, and the isotopic characteristics of zircon’s intrinsic chemical structure. Interestingly, two pieces of significant information about the ancient days of planet Earth are attributed directly to the analysis of zircon crystals: some zircons from the Narryer Gneiss Terrane dated to 4.4 billion years ago contain isotopes of oxygen which suggest that liquid water may have already been present on the surface of the Earth during their formation, and some zircons from this same region dated to approximately 4.1 billion years ago contain traces of carbon isotopes associated with the biological process known as “enzymatic carbon fixation”, suggesting that living beings were already present and active during that period of Earth’s history.
A zircon crystal from the Mud Tank Zircon Field in Australia’s Northern Territory; Image: Mindat/ Rob Lavinsky
Cross-section of a zircon crystal showing the its layered growth structure; Image: Wikipedia
© Yaĝé Enigmus
]]>Zircon makes another early appearance in history as part of an ancient Hindu poem which describes the magical Kalpa Tree: a mystical tree said to have leaves made of beautiful zircon gems which was given to Earth as a gift from the Gods.
Zircon gemstones were also used in Hindu cultures in place of hessonite garnet as these two gemstones were sometimes confused for one another since they could both exhibit some of the same brown, orange, and red hues, occasionally displaying a similar lustre as well.
A “hyacinth” zircon crystal on calcite matrix from the Astore Valley in Gilgit-Baltistan, Pakistan, showing zircon’s typical pyramidal terminations; Image: Mindat/ Joseph A. Freilich
Hinduism places importance on nine celestial deities, and these deities are additionally represented by nine gemstones known as the “navratna”, literally meaning “nine gems” or “nine jewels”, which includes blue sapphire, yellow sapphire, ruby, emerald, diamond, pearl, coral, cat’s eye chrysoberyl, and hessonite garnet, with the celestial deity of Rahu (i.e. “the ascending lunar node”) being associated with hessonite garnet, known in Hindi as the “gomed” stone; it has been determined that some gomed gems of earlier eras were actually zircon gemstones which had been confused for hessonite garnet. To this day brown zircons are on rare occasions used as a substitute for hessonites in the navratna when hessonite is unavailable or no hessonites of sufficiently high quality can be found; gems used as part of the navaratna must be high enough quality called to be considered “joytish” gemstones, a term meaning “the science of light” or “the science of heavenly bodies”.
A navaratna-style ring with (beginning at the top centre and going clockwise) dark blue sapphire representing the deity Shani (i.e the Saturn), cat’s eye chrysoberyl representing the deity Ketu (i.e. the Descending Lunar Node), yellow sapphire representing the Brhaspati (i.e. Jupiter), emerald representing the deity Budha (i.e Mercury), diamond representing the deity Shukra (i.e. Venus), pear representing the deity Chandra (i.e. the Moon), coral representing the deity Mangala (i.e. Mars), hessonite garnet representing the deity Rahu (i.e. the Ascending :Lunar Node), and ruby (centre) representing the deity Surya (i.e. the Sun); Image: Wikipedia
The mineral zircon is an important part of the Earth’s crust and occurs in almost all igneous rock formations, often forming as a result of magmatic activity; due to their high melting point, zircon crystals are usually among the first minerals to precipitate from molten stone. Zircon is also frequently found in metamorphic rocks as its high heat resistance allows it to survive the metamorphosis of preexisting igneous rocks; in addition to this, zircon is common in sedimentary rocks as it frequently collects in sediments and sands due to its high specific gravity and resistance to weathering. Despite its nearly ubiquitous presence in rocks across the Earth, zircon crystals found in most rocks are typically quite small, often being less than 0.3mm in diameter; zircon crystals of suitable size for cutting into gemstones are actually rather rare in nature. The majority of non-gem-grade zircon which is actively exploited from larger deposits is used for industrial applications, with Australia and South Africa accounting for over two thirds of the world’s industrial zircon production; an exceptionally tiny fraction of non-gem-grade zircon is used in scientific research. A handful of geographic locations have produced gem-quality zircon, although the yield from these sources is usually somewhat small when compared to what is typical for many mines which produce other coloured gemstones. Some of the most important sources for zircon gems include Thailand, Cambodia, and Sri Lanka, with other notable sources including Australia, Tanzania, Nigeria, Madagascar, Vietnam, and Pakistan.
A brown zircon crystal from the Mogok Mining District in the Mandalay Region of Myanmar (a.k.a Burma); Image: Mindat/ Harald Shillhammer
As an industrial material, zircon has a number of useful applications. Zircon is the primary ore from which zirconium metal is obtained, which is an important alloying metal in the production of surgical instruments and certain light filaments because of its resistance to corrosion. Zircon is also the primary source for the compound zirconium dioxide (ZrO2), which is used in some abrasive products, and due to its high melting point over 2,700°C (4,900°F) it is employed as a refractory material in laboratory crucibles and metallurgical furnaces. In addition to these derivative products, zircon itself is directly utilised by parts of the ceramics industry where it is used to add opacity to ceramic preparations.
Industrial zirconium dioxide (ZrO2) powder; Image: Wikipedia
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]]>A round brilliant cut cubic zirconia gemstone; Image: Wikipedia
A pair of 14 karat white gold studs featuring natural “matara diamond” colourless zircon gemstones; Image; Skyjems
The term “zirconia” is another name for zirconium dioxide (ZrO2), which was originally discovered as the mineral baddeleyite in 1892, although this mineral is not analogous to “cubic zirconia” as they have different crystal structures. All crystalline materials can be organised into one of seven crystal systems based on the geometry of their internal structure. These systems are: monoclinic, triclinic, orthorhombic, tetragonal, cubic, hexagonal, and trigonal crystal systems, although the trigonal system is often grouped together with the hexagonal system as the former can be geometrically encompassed by the latter; the mineral baddeleyite falls into the monoclinic crystal system, while the aptly named cubic zirconia falls into the cubic crystal system.
Simplified diagrams of the geometries found in the six major crystal systems; Image: geology In
A large crystal of baddeleyite on matrix from Phalaborwa in Limpopo, South Africa; Image: Mindat/ Rob Lavinsky
Zirconia with a cubic crystal structure was first encountered in 1927 as a synthetic product called “stabilised zirconia”, but at first this lab-gown substance was merely a form of crystalline ceramic that had applications as a refractory material. In 1937, naturally occurring zirconia crystals with a cubic structure were discovered by German mineralogists as microscopic inclusions in samples of natural zircon (ZrSiO4) alongside inclusions of baddeleyite; the tiny inclusions were distinguished from baddeleyite with x-ray crystallography, but they were not considered significant beyond the fact that they proved synthetic cubic zirconia did have a natural counterpart, and they consequently received little attention from most scientists. Synthetic cubic zirconia did however gain traction in the scientific community as a useful material in optical research, where it eventually outpaced the use of other synthetic crystals, like yttrium aluminium garnet, gadolinium gallium garnet, synthetic rutile, and synthetic strontium titanate.
Individual crystals of cubic zirconia suitable for optical applications were difficult to grow, and production of such crystals did not accelerate until the 1960’s when melt growth techniques were heavily investigated in France, although these methods initially only yielded small crystals. Soviet scientists developed a successful technique for growing larger crystals called ”skull crucible”, which was published in 1973 and paved the way for the commercial production of cubic zirconia that began in 1976. By 1977, cubic zirconia was being mass-produced for use in the jewellery industry as a diamond simulant. Annual worldwide production of cubic zirconia gemstones had reached approximately 60 million carats by 1980, and it had grown to over 33 times that amount by 1998 following the development of the “skull-melting” method, which was patented by Josep F. Wenkus in 1997 and remains the primary technique for producing gem quality cubic zirconia to this day. The flood of synthetic cubic zirconia gems into the jewellery market has only caused further confusion among buyers surrounding natural zircon (ZrSiO4) gemstones due to strong similarities in name between these two materials, cementing the idea in many people’s minds that the term “zircon” refers to cheaper laboratory grown stones rather than natural Earth-mined gems.
As a gemstone, cubic zirconia (ZrO2) strongly resembles diamond (Cx) and zircon (ZrSiO4) gemstones due to its high dispersion value and diamond-like lustre; cubic zirconia actually has greater dispersion or “fire” than diamonds (0.058-0.066 vs. 0.044) which does give the stone an attractive appearance, but when compared to diamonds and zircon the fire of cubic zirconia is so strong that it may seem unnatural to the discerning eye. The refractive index of diamond is higher than cubic zirconia, so the latter does not show as much brilliance as the former, and cubic zirconia’s hardness is also lower than that of diamond, ranking at 8-8.5 on the Mohs Hardness Scale, whereas diamond ranks at 10 as one of the worlds hardest materials. The lower hardness of cubic zirconia gemstones causes them to be abraded more easily than diamonds and consequently need repolishing or replacement on a more frequent basis, however the hardness of zircon (Mohs 6-7.5) is even lower than cubic zirconia, a factor which contributed to cubic zirconia’s replacement of zircon in the 20th Century as the primary diamond simulant.
Colourless and pink cubic zirconia gemstones; Image; GIA/ Tino Hammid
There was an initial advantage that zircon (ZrSiO4) had over cubic zirconia (ZrO2): its colour. In the earliest days of cubic zirconia use within the jewellery industry, only natural white zircons were replaced by this synthetic material, while natural coloured zircons could still be used in ways that cubic zirconia could not. Very quickly after its introduction, cubic zirconia gemstones which displayed different hues were developed by doping growth solutions with additional metals, the same method used for producing coloured synthetic corundum, coloured synthetic spinel, and other coloured synthetic gemstones. For cubic zirconia, cerium (Ce) dopants induced orangish hues, chromium (Cr) and Vanadium (V) dopants induced green hues, nickel (Ni) and thulium (Tm) dopants induced brownish hues, erbium (Er) and europium (Eu) dopants induced pink hues, cobalt (Co) and neodymium (Nd) dopants induced purplish hues, iron (Fe) and holmium (Ho) dopants induced yellowish hues, titanium (Ti) dopants induced golden hues, copper (Cu) dopants induced yellow and bluish hues, manganese (Mn) dopants induced brown and/or violet hues, and praseodymium (Pr) dopants induced amber hues. By giving cubic zirconia (ZrO2) gemstones the ability to display a colour range as diverse as that of natural zircon (ZrSiO4), these synthetic gemstones further overshadowed zircon gems in the jewellery trade, leading to the grossly underappreciated profile of natural zircon that is prevalent today.
A series of different coloured cubic zirconia crystals; Image: GIA/ Ceres Corporation
A variety of different coloured cubic zirconia gemstones; Image: GIA/ Ceres Corporation
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A faceted blue zircon gemstone from Cambodia which has been enhanced with heat treatment; Image: Skyjems
There exist zircon gemstones which show a colour change effect similar to the phenomenon seen in alexandrite gems, where the apparent hue of a gem changes considerably depending on the lighting conditions under which it is viewed. For zircon, this colour change frequently presents as an apparent bluish purple or greyish purple colour when the stone is viewed in natural daylight conditions, and an apparent green hue when the stone is viewed under fluorescent and/or warm-toned lighting conditions. The exact cause of this phenomenon in
zircon is not known, but spectroscopic analysis indicates that uranium (U) is likely involved in some way. Many of the colour changing zircon gemstones which have been found to date are attributed to the Mogok Mining District of Myanmar’s Mandalay Region, and the majority of these stones only displayed the colour change effect after they were subjected to high temperature treatment. In very rare cases, zircon gemstones may contain parallel inclusions which reflect light and produce a chatoyant lustre; such gems may then exhibit a “cat’s eye” effect if cut en cabochon.
Two faceted zircon gemstones from Myanmar (a.k.a Burma) showing in daylight conditions (left) and incandescent light (right); Image: Swiss Gemmological Institute
Synthetic zircon has been produced under laboratory conditions by using the flux growth method, with the addition of quadrivalent vanadium (V4+) and quadrivalent uranium (Ur4+) each separately producing stones which display bluish hues. Even though synthetic zircon can be grown in a laboratory, such stones never reach the jewellery market; one would be much more likely to encounter synthetic corundum and/or synthetic spinel being passed off as imitation zircon. In recent decades the use of synthetic corundum and synthetic spinel as replacements for natural zircon has become extremely uncommon, and another synthetic material has instead taken their place: cubic zirconia.
A faceted blue cubic zirconia gemstone; Image: GIA/ Robert Weldon
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Yellow zircon crystals on matrix from the Poudrette Quarry in Mont Saint-Hilaire, Quebec Canada; Image: IGS/ Modris Baum
As a zircon crystal is further damaged by radiation and becomes less crystalline, the refractive index, birefringence, specific gravity, and mohs hardness of the material decrease. In addition to changes in these properties, the apparent brilliance of zircon diminishes as its crystal structure becomes further damaged, and in many cases stones which are fully amorphous in structure will appear cloudy or hazy. Zircon which has completely lost its crystalline structure is described as “metamict”. Curiously, the dispersion value of zircon does not change in response to the metamiction process. In the field of gemology, zircon gemstones are grouped into three separate categories or “types” based on the amount of metamiction they have undergone: “high” or “normal” type zircons are fully crystalline, “intermediate” or “medium” type zircons are partially amorphous, and “low” type zircons are considered to be fully metamict; the terms “alpha”,”beta”, and “gamma” are also sometimes used to describe these three categories. Subjecting zircon to high temperature treatment can cause stones to recrystallize, thus repairing radiation induced damage present in zircon’s crystal structure; in such cases medium type and low type zircons can be converted back to high type zircons.
Zircon Type |
Refractive Index |
Birefringence |
Specific Gravity |
Mohs Hardness |
High |
1.92 - 2.01 |
0.036 - 0.059 |
4.60 - 4.80 |
7 - 7.5 |
Medium |
1.83 - 1.97 |
0.008 - 0.043 |
4.08 - 4.60 |
6.5 - 7.5 |
Low |
1.78 - 1.82 |
0.000 - 0.008 |
3.93 - 4.20 |
6 - 6.5 |
One of many varicoloured gemstones, zircon gems are available in a wide range of hues. Orange, red, yellow, brown, green, blue, pink, peach, and colourless zircons are all found in today’s jewellery market, with blue, red, and green stones being among the most valuable.
Faceted zircon gemstones of various colours; Image: Gemological Institute of America
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Species |
|
Chemical Formula |
ZrSiO4 |
Mohs Hardness |
6 - 7.5 |
Cleavage |
Indistinct |
Lustre |
Vitreous to Adamantine |
Refractive Index |
1.78 - 2.01 |
Birefringence |
0.000 - 0.059 |
Dispersion |
0.039 |
Pleochroism |
Weak to Distinct |
Specific Gravity |
3.93 - 4.80 |
The name “zircon” will sound familiar to many people, but this splendid natural gemstone receives significantly less attention than it deserves despite the fact that zircon gems are an important part of the contemporary jewellery trade. The mineral form of zirconium silicate (ZrSiO4), this somewhat rare gemstone has been sought after by human beings for thousands of years, and it continues to add flare to the jewellery designs of today which is not easily rivalled by other coloured gems. The English name for zircon comes from the German word “zirkon”, which is thought to be derived from the arabic word “zarkun” meaning “vermillion”, although some academics believe that the Persian word “zargon” meaning “golden” is the source of zircon’s name; zircon gemstones may be golden or vermillion among other colours, so both “zarkun” and “zargon” are equally plausible roots of the word “zirkon”. With its diverse range of hues and variable optic character, there exists a zircon gemstone for nearly every gem lover and jewellery enthusiast.
A faceted blue zircon gemstone from Cambodia; Image: Skyjems
Some of zircon’s most desirable properties are its high refractive index, high dispersion, and strong lustre. Zircon typically refracts, i.e. “bends”, light much more than the majority of well known gem varieties, and zircon’s dispersion value of 0.039 is significantly higher than most other coloured gemstones, even approaching diamond’s dispersion value of 0.044. These characteristics, in combination with its potential to show an adamantine or “diamond-like” lustre, make zircon an aesthetic rival to diamond. The similarities between diamond and zircon gems are particularly apparent when comparing stones that are completely colourless, and this resemblance is even more obvious if the stones being compared have been given a round brilliant cut. Although very similar looking to the naked eye, zircon gemstones can often still be separated from diamonds due to their high birefringence, which causes a double refraction of light passing through them, giving the inside of gems a doubled or blurry appearance. The birefringence of zircon is highly variable though and not all zircon gems display readily visible double refraction, but diamonds will never exhibit this same phenomenon. Zircon and diamond can also be easily distinguished from one another by differences in their hardness; the hardness of zircon is markedly lower than that of diamond, ranging from 6 to 7.5 on the Mohs hardness scale as opposed to 10. In addition to its lower hardness, zircon is also quite brittle in tenacity.
A faceted brown-orange zircon gemstone; Image: Skygems
The higher end of zircon’s hardness may be more suitable for certain jewellery pieces, but the potential for zircon gems to rank as low as 6 in hardness in addition to zircon brittle nature means jewellers must be mindful when creating bespoke jewellery designs that feature zircon gemstones. These characteristics of zircon would preclude some zircon gemstones from being used in custom engagement rings or other everyday ring designs, as zircon gems of lower hardness would scratch more easily, and their facet junctions would be prone to chipping due to zircon brittleness. Similarly, zircon gems set into everyday bracelets are at greater risk of being damaged. zircon gemstones are best suited for use in rings and bracelets worn only occasionally, but zircon can be worn every day almost carefree in earrings and/or pendants. The durability of zircon would make the use of ultrasonic cleaners unadvisable for jewellery featuring zircon gems, and it is recommended that bespoke ring and bracelet settings meant for zircon be designed with a protective structure to shield stones from direct impacts and/or abrasions.
A faceted dark red zircon gemstone; Image: Skyjems
A curious product of nature, zircon gems vary in more ways than just their colour. In the next part of this series, learn about the ways in which zircon gems may differ from one another in colour and character.
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