Ruby and Sapphire: Gems of the Mineral Corundum Home » Gemstones » Ruby and Sapphire Ruby and Sapphire Ruby and sapphire have the same chemical composition and crystal structure - they are both varieties of the mineral corundum Rubies: The most desired variety of corundum is the ruby. The red color is produced by trace amounts of chromium in the mineral. These two beautiful rubies were mined in Madagascar. The one on the left is a 7 x 5 millimeter octagon that weighs about 1.32 carats. The one on the right is an 8 x 6 millimeter oval that weighs about 1.34 carats. Although Asia has been the traditional source of gem corundum for over one thousand years, Africa is poised to become a new primary source. Ruby, Sapphire, and Fancy Sapphire Most people don't realize that ruby and sapphire are both gems of the mineral corundum . Both of these gems have the same chemical composition and the same mineral structure. Trace amounts of impurities determine if a gem corundum will be a brilliant red ruby or a beautiful blue sapphire. It is surprising that "impurities" can produce such wonderful results!

Red and blue are just two of the many colors found in gem corundums. Trace amounts of other elements can produce brilliant yellow, orange, green, and purple gems. Red corundums are known as "rubies," blue corundums are known as "sapphires," and corundums of any other color are known as " fancy sapphires ." Corundum produces gems in a spectrum of colors. Related: Corundum: Mineral Summary What Makes a Ruby? Some gem-quality corundum contains trace amounts of chromium. A very small amount of chromium gives corundum a pink color. Larger amounts of chromium increase the color saturation of the stone and produce a gem with a deeper red color. To be considered a "ruby," a corundum should have a color between orangey red and a slightly purplish red. The most desirable color is a pure vibrant red. Very few specimens of corundum have a natural color within the range required for a ruby. Very few also have the clarity required to produce a nice faceted stone. Long ago, people who prepared gem materials for cutting discovered that heating rubies under controlled conditions can intensify their color.

Heating can also cause inclusions to become less visible and improve the clarity of a gem. Most rubies in the market today have been heated to improve their color and clarity. Many of them have had other treatments to improve their appearance. These treatments are normal and expected in the gem trade, but a seller should disclose them to a buyer in advance of a sale. Montana sapphire: The most widely known sapphire locality in North America is Yogo Gulch, Montana, famous for producing deep blue sapphires of excellent quality. Creative Commons photo of a gem from Barnes Jewelry, Helena, Montana, by Montanabw. Corundum as ruby, sapphire, and fancy sapphire: Gem-quality corundum is a highly prized and valuable material. When it is bright red in color, it is called "ruby." When it is deep blue, it is called "sapphire." Gem-quality corundum of any other color is called "fancy sapphire." All of the stones in this photo were mined in Africa. What Makes a Sapphire? Trace amounts of iron and titanium can develop a blue color in corundum.

Blue corundums are known as "sapphires." The name "sapphire" is used for corundums that range from light blue to dark blue in color. The blue can range from a violetish blue to a greenish blue. Stones in the middle of this range, with a rich blue color, are the most desirable. Gem-quality corundum occurs in a wide range of other colors, including pink, purple, orange, yellow, and green. These stones are known as "fancy sapphires." It is surprising that a single mineral can produce gemstones of so many different colors. When the color of a sapphire is any color other than blue, the color should be used as a preceding adjective to describe the stone. For example, pink sapphire, yellow sapphire, or green sapphire. Used alone, the word "sapphire" refers only to blue corundum. The color and clarity of blue and fancy sapphires can be altered by heat, radiation, and other treatments. Sometimes pale, milky, cloudy, or translucent stones can be heated to yield stones that are brighter in color and more transparent.

If such treatments have been used, sellers should disclose the types of treatments to potential buyers when the stone is presented for sale. Ruby on marble: A ruby crystal on white marble from Jegdalek, Saroby, Afghanistan. This crystal is about 1.6 centimeters in length. Specimen and photo by Arkenstone / . Sapphire crystal: A blue, doubly terminated, translucent sapphire crystal from Sri Lanka. Most crystal specimens like this have been transported by streams and show a greater amount of wear. This specimen has not been treated. Heat treatment would likely deepen the color, make it more uniform, and improve the clarity. This crystal is about five centimeters in length. Specimen and photo by Arkenstone / . Popularity of Ruby and Sapphire Ruby and sapphire are extremely popular gemstones. Virtually every jewelry store that features colored gemstones in jewelry will have a generous portion of their display dedicated to ruby and sapphire items. Ruby is the most popular red gemstone, and sapphire is the most popular blue gemstone.

The pie chart below shows the share of colored stone imports on a dollar value basis that went to the categories of sapphire, ruby, emerald, and all other gemstone varieties during the 2011 calendar year. It shows that sapphire and ruby were the second and third most imported colored stones during that year. A total of $282 million worth of sapphire was imported, and a total of $45 million worth of ruby was imported. Colored stone imports: This chart illustrates the popularity of sapphire and ruby in the United States. The pie represents all colored stones imported into the United States during 2011 on the basis of dollar value. As single gem varieties, sapphire and ruby hold major positions in the import market, accounting for over 35% of all colored stones imported and a total value of approximately $400 million. Data is from the USGS Minerals Yearbook, April 2013. [5] Although the pie chart above does not include domestic colored stone production, it can be considered as nearly complete.

The United States Geological Survey estimates that the value of the total domestic production of colored stones of all kinds in the United States during calendar year 2011 was only $11 million. Related: Emerald: The Most Popular Green Gem Synthetic star ruby: Laboratories have been able to mass-produce synthetic star corundum since the Lindy division of Union Carbide flooded the gem market with them in the 1950s and 1960s. This synthetic red corundum has a visible six-ray star and a faceted back to enhance the base color of the stone. Star sapphire: Some specimens of sapphire and ruby contain a very fine "silk" of fibrous inclusions that parallel the crystallographic axes of the mineral. When these stones are cut into a cabochon with the c-axis of the stone penetrating the base of the stone at right angles, a six-rayed star can be seen floating on the surface of the cabochon. These are known as "star sapphires" or "star rubies," according to their color. Public domain photography by Mitchell Gore.

Mining Rubies and Sapphires Most gem-grade corundum forms in metamorphic rocks such as schist or gneiss and igneous rocks such as basalt or syenite. However, gem corundums are rarely mined from the rocks in which they form. Mining small gems from hard rock is possible, but it is very expensive, and many of the gems are broken during the mining process. Fortunately, corundum is very hard and resistant to weathering. In many areas, natural weathering and erosion have liberated the stones and carried them into streams over long periods of geologic time. Today, the gems are mined from these stream sediments. Their high specific gravity relative to other sediment particles often causes currents to concentrate them in small placer deposits. Most rubies and sapphires are produced by washing the gravels of these stream deposits. This work is often done by hand because the deposits are small and irregular in shape and character. These deposits are often located in countries when wages are very low and artisanal mining is prevalent.

Noteworthy locations where gem-quality corundums have been produced include Myanmar, Thailand, Cambodia, Vietnam, India, Pakistan, Afghanistan, Sri Lanka, China, Australia, Madagascar, Kenya, Tanzania, Nigeria, and Malawi. Blue star sapphire: A deep blue star sapphire 8 mm x 6 mm cabochon from Thailand. Inclusions within the stone align with the crystallographic axis to produce the star - which is only clearly visible and centered when the back of the stone is cut at 90 degrees to the c-axis of the crystal. This stone has been heat treated to darken the stone and enhance the visibility of the star. Ruby and Sapphire Information [1] Gems: Their Sources, Descriptions and Identification: Michael O’Donoghue; Elsevier; sixth edition; 873 pages; 2006. [2] Gemstones of the World : Walter Schumann; Sterling Publishing; fifth edition; 320 pages; 2013. [3] Rubies and Sapphires : Fred Ward; Fred Ward Gem Books; 65 pages; 2010. [4] Rock and Gem : Ronald L.

Bonewitz; The Smithsonian Institution, Dorling Kindersley Publishing; 360 pages; 2008. [5] 2011 Minerals Yearbook: Gemstones : Donald W. Olson; The United States Geological Survey; 22 pages; 2013. Synthetic Corundum as an Essential Product Rubies and sapphires have been highly sought after in many parts of the world for over one thousand years. Deposits that produce high-quality stones of good color have attracted enormous amounts of attention and have been heavily exploited. As a result, buyers who need large quantities of quality stones are having a harder time finding them in the volumes needed for today's jewelry marketplace. Let's imagine a jewelry manufacturer who wants to create enough matching ruby pendant, ring, and earring sets to supply a large jewelry chain with thousands of stores and a busy internet site. This manufacturer will need at least four nice rubies for each matching set, multiplied by enough sets to supply thousands of stores and a busy internet site. This manufacturer will need millions of rubies, all color-matched into sets and all cut into calibrated shapes and sizes.

On the production side, the labor needed to discover, mine, grade, cut, and polish these stones will be enormous. An enormous effort will also be needed on the manufacturing side just to find enough sellers to provide them, confirm their quality, negotiate prices, make large numbers of purchases, and deliver the stones to the manufacturing facility. The problem of sourcing gemstones to meet the needs of a large manufacturing company is so much simpler if the stones themselves are manufactured. This is why laboratories capable of reliably producing synthetic rubies and sapphires of consistent size, color, grade, and appearance have found an important place in the gemstone market. If you go shopping in the United States and look at the ruby and sapphire jewelry offered in many famous-name mall jewelry stores and department stores in the $50 to $500 price range, you will find that many of the jewelry items are made using "created" or "synthetic" rubies and sapphires. The synthetic corundum in this jewelry is perfect in color, has wonderful clarity and is extremely attractive. Many shoppers see the lower price and better appearance of the synthetic materials when compared to natural stones of similar size and opt to purchase the synthetic.

It is a logical choice based upon what appeals to the person and what they are willing to pay. They get great appearance at a lower price. Natural gemstones are a finite resource that will become more difficult to obtain and more expensive over time. As a result, buyers will probably see more synthetic stones offered in most jewelry stores and should expect to see the price difference between synthetic stones and natural stones of similar size, color, and quality become greater in the future. Many consumers prefer natural stones, and many also make the decision to purchase synthetic stones. That follows the often-given advice of "buy what you like and can afford." Corundum: The mineral Corundum, Sapphire, Ruby info & pictures Advertising Information The Mineral corundum Corundum is best known for its gem varieties, Ruby and Sapphire. Ruby and Sapphire are scientifically the same mineral, but just differ in color. Ruby is the red variety, and Sapphire is the variety that encompasses all other colors, although the most popular and valued color of Sapphire is blue. Sapphire is also only used to describe the gem variety; otherwise it is simply called Corundum. Corundum is a very hard, tough, and stable mineral.

For all practical purposes, it is the hardest mineral after Diamond , making it the second hardest mineral. It is also unaffected by acid s and most environments. Translucent brown Corundum and Emery are the most common forms of Corundum. These are fairly common forms, and due to their great hardness and prevalence are the most favorable abrasive s. The industrial term "emery" describing Corundum abrasives is derived from the variety Emery which is mined specifically for its use as an abrasive. Erosion may cause Emery to crumble and form sand, which are sometimes called "black sands." Corundum is easily synthesized , and many Corundum abrasives are synthetic. Synthetic gems are also easily created by adding traces of certain color producing elements to the Corundum solution, and letting the solution solidify into a boule , or synthetic, unprocessed "mineral" with a particular shape. This process is called the Verneuil process . Natural Ruby and Sapphire gemstone s may have their color artificially enhanced or deepened through heat treatment when used as gems. Some dark blue stones from certain localities may also be made a bright blue desirable color. USES Ruby and Sapphire are the most famous gemstones after Diamond .

They have retained their high value throughout the centuries and are continuously and vigorously mined throughout the world. Red rubies and blue Sapphires are the most popular Corundum gemstones, though other Sapphire colors such as orange, yellow, and green are becoming increasingly popular in gemstone use. Corundum has some electrical uses, and non gem material, such as Emery , is used as an abrasive because of its high hardness . The gemstone applications of the Corundum varieties are discussed in greater detail in their own dedicated gemstones pages. Make sure to also see the gemstone section on Ruby and Sapphire . NOTEWORTHY LOCALITIES The area of Mogok, Burma (Myanmar) is the source of some of the best gem -quality Ruby . Another significant Burmese deposit is Mong Hsu, which is currently a major Ruby producer, though its color isn't as fine as the Mogok material. Sri Lanka, especially the area of Ratnapura, Bibile, and Rakwana, is an excellent source of gem quality Corundum of all colors. The finest and largest crystallized specimens and aggregate s of gem-quality Sapphire are from Sri Lanka.

Ruby with a brownish tint comes from Thailand, in the Chantaburi District. Fine gem Ruby and Sapphire comes from Luc Yen, Yenbai Province, Vietnam; the Hunza Valley, Gilgit, Pakistan; and Jegdalek, Sorobi District, Afghanistan. Gem quality Sapphire is well-known at Pailin, Cambodia. Translucent to opaque Ruby, sometimes with asterism , is very abundant at Mysore (Mysuru) and Subramanium, in Karnataka, India. Africa has recently become a significant producer of Corundum, especially in Madagascar, where it is found in the Zazafotsy Quarry, Ambahatraso; and in Andranondambo, Amboasary District. A famous African locality in which opaque rubies are found in green Zoisite is is in Longido, Kilimanjaro Region, Tanzania. Another important Tanzanian Ruby mine is Winza, in Arusha. In the U.S., the Yogo Gulch in Judith Basin Co. has produced choice, deep blue Sapphire crystals. Not far from the Yogo Gulch, near Helena, waterworn Sapphires stones are found in the Missouri River throughout its length in Lewis and Clark County.

Montana is also the claim to a few other localities: the Gallatin Gateway and Salesville, Gallatin Co.; Rock Creek, Granite Co.; and Cottonwood Creek, Deer Lodge Co. In California, well-formed, elongated Corundum crystals were found in Cascade Canyon in the San Gabriel Mountains, San Bernardino Co. A well known Ruby locality is the Cowee Creek District, Macon Co., North Carolina, especially the area of Franklin. Large deposits of Emery were once worked near Peekskill, Westchester Co., New York; and Chester, Hampden Co., Massachusetts. An important Canadian occurrence of Corundum is the Burgess Mine, Bancroft, Hastings Co., Ontario. Ruby and Sapphire Ruby and Sapphire: Varieties of Corundum Corundum Corundum, an aluminium oxide, Al2O3, is 9 on the hardness scale. It is in the trigonal subdivision of the hexagonal crystal system, which is reflected in the commonly found hexagonal prismatic crystal form. Corundum has no cleavage, but conchoidal or splintery fracture. It is transparent to translucent and has a vitreous to nearly adamantine luster.

The specific gravity is high, 3.97-4.05. Corundum is doubly refractive, 1.762-1.778, with definite to strong pleochroism. Rutile, with an acicular habit, is a common inclusion that creates a chatoyancy, cat's eye effect, or asterism when the gem is oriented and cut properly. In a pure state corundum is colorless, but can also be red, blue, pink, orange, yellow, green, purple, and black. Gem quality red corundum is known as ruby, whereas any other color is termed sapphire. Ruby occurs in metamorphic rocks, dolomitic marble and gneiss, whereas sapphire may be found in sedimentary limestones, metamorphic marble, and igneous basalt, pegmatites, or andesite dikes. Corundum is very rarely mined from primary deposits, but typically mined from secondary alluvial or placer deposits, where this resistant mineral becomes the sand and gravel of stream beds. Ruby and sapphire have been synthesized since the end of the 19th century for industrial and gem quality uses.

Synthetic star ruby and sapphire have been marketed since 1947. Sapphire from Urals, Russia, 10x8 cm. Image taken from David Barthelmy's , Mineralogy Database Amethyst Mineral Galleries Inclusions Solid crystal inclusions found within corundum include apatite, calcite, chlorite, corundum, fluorite, graphite, olivine, pyrite, quartz, spinel, tourmaline, and zircon, to name a few ( Hughes ). Other inclusions include liquid/gas/solid filled cavities, that create "wispy" patterns, which may be confused with flux inclusions of synthetics; growth zoning, which are straight lines that follow the angular, hexagonal pattern reflecting the crystal system and form; and exsolved solid inclusions such as rutile needles and hematite-ilmenite plates. The exsolved rutile inclusions are called "silk" and are oriented in three directions at ~60/120° in the basal plane.

Treatments Although gem treatment and enhancement probably go back several thousand years, modern methods for heat treating sapphire rough arrived by 1920, with ovens capable of reaching the necessary temperatures of over 1500° C ( Hughes ). Virtually all rubies and sapphires sold today are heat treated for color and clarity enhancement, with the exception of stones mined prior to 1975, that have not been subsequently treated ( Hughes ). Image taken from Tradeshop Inc Geographic Sources Some likely localities for corundum are given at mindat.org . Hughes wrote on, Myanmar (Burma) and India , along with specific pages on the Mogok ruby and Burmese sapphires . In addition to the more famous US sapphire sites in Montana, another location is found in Minnesota, according to the web authors at the University of Minnesota, Duluth. Pricing Colored stones, such as ruby and sapphire, lack a universally-accepted system of quality analysis needed to arrive at logical price structures. Hughes provides specific information on ruby and sapphire prices . Image taken from Jewelry Central . Ruby Ruby is the July birthstone and 15th and 40 anniversary stone.

For specific birthstone information, visit: July birthstone: Ruby, jewelrycentral.com . Finely colored rubies are one of the most expensive of all gems, with the exception of rare colored diamonds. Because natural flawless ruby is virtually unheard of, synthetics are usually easy to spot! Visit Ramaura Cultured Ruby , at J.O. Crystal and Chatham created ruby for details. In addition to synthetics, common ruby imitators (The Jewelry Experts Bijoux Extraordinaire, Ltd.) are spinel, rubellite tourmalines and pyrope garnets. In addition, garnet may be misrepresented as Almandine ruby, Australian ruby, Bohemian ruby, and Cape ruby, while spinel may be called Balas ruby and Ruby spinel. Tourmaline may be referred to as Siberian ruby. It was not until 1800 that ruby was recognized as a separate mineral; prior to 1800 red spinel and red garnet were designated as ruby, from the Latin rubens which means red ( Schumann , 1997, p. 82).

Chromium is the coloring agent for ruby and the "pigeon's blood" is a desirable color, red with a overtone of blue. Image taken from The Mineral and Gemstone Kingdom Famous rubies (Coyle Wholesale Jewelers), distinguished because of their size or extraordinary beauty, are located in various museums and private collections. For example, the 167-carat Edwardes Ruby, named in honor of Major-General Sir Herbert Benjamin Edwardes (1819-68) who served for the British in India, is located in the British Museum of Natural History. The Smithsonian has the 137-carat Rosser Reeves Ruby, a star ruby, while the American Museum of Natural History has the 100-carat Edith Haggin de Long Ruby. The famous Black Prince's Ruby and Timur Ruby, both part of the British Crown Jewels, are in fact red spinels. The Smithsonian has a most spectacular star ruby over 138 carats, the Rosser Reeves Ruby, as well as a recent acquisition of the largest faceted ruby in their collection, mineralsciences.si.edu/collections/newacquisitions/2004/carmenlucia.htm .

Indian Star Ruby The Mineral and Gemstone Kingdom Sapphire Sapphire is the September birthstone and for the 5th and 45th anniversary gemstone gifts. For specific birthstone information, September birthstone, Sapphire, jewelrycentral.com . Sapphire comes in all colors except red! It may be colorless, a deep blue, green, golden yellow, pink, reddish-orange, and violet. The most valuable color of sapphire is referred to as "corn-flower blue;" black, grey, or green overtones to this vivid blue will reduce overall value. Blue sapphire is not as expensive as diamond, emerald, and ruby, with the exception of the rare variety called Padparadscha, an orange-pink stone, and some pink stones. Pink Sapphire and Gemstone Kingdom Needle-like, rutile inclusions in saphhire can be desirable when the gem is cut in a cabochon shape and asterism results! A six-rayed white star appears in bright lighting and the quality is judged by sharpness of star, symmetry of the rays, and the body color. The blue or black body color is host to the asterism in these images.

Famous sapphires include the 543-carat "Star of India," possibly the largest cut star sapphire, and the "Midnight Star," a black star sapphire, both housed at the American Museum of Natural History in New York City. The St. Edward's and Stuart sapphire are part of the British Crown Jewels and the Smithsonian owns the 330 carat "Star of Asia." See Coyle Wholesale Jewelers for more detail on famous sapphires . Black Star Sapphire The Mineral and Gemstone Kingdom In times past, any blue gem material was called sapphire, such as lapis lazuli. Sappheiros is Greek for "blue." In order for sapphire to be that desired blue and other valuable colors, it has been estimated that 99.9% of all sapphire is heat treated to improve color and clarity. Visit Chatham Created Gems for details about created blue saphhire . Image was taken from Rubies and Sapphires Rubies and Sapphires Rubies and Sapphires by Fred Ward. Fourth edition. From the Fred Ward Gem Book Series. Rubies and sapphires are the two gem varieties of the mineral corundum.

These precious stones are among the most valuable and desirable gems on the market. They are cut into beautiful faceted stones and wonderful cabochons that display a variety of opical phenomenon. Fred Ward tells you the history of these gemstones, how they are mined, how they are evaluated and how they are cut. Included is a description and history of lab-grown stones and simulants. He also gives great advice on how to buy them and how to properly care for them. Loaded with fantastic photos. This book is a 6" x 9" paperback with 65 pages. Only $19.95 How rubies are formed Home > Earth > Gemstones > Sapphires and Rubies Gifts from the Earth: Sapphires and Rubies The word sapphire comes from the Greek "saapherios", which means blue. These are the blue gemstones most often seen in jewelry, with colors ranging from pale, ice blue to deep, cobalt blue, but did you know that sapphires also come in other colors? Blue is just the more highly prized variant of the mineral corundum. Sapphires also come in orange-pink, golden, white, and even black.

The natural crystal form of sapphire is called a trigonal (three-sided prisms), examples of which are in the photo below. Some more interesting varieties of sapphire with rutile (the ore form of titanium) intrusions cause light to be reflected in a six-point star, creating what is known as a star sapphire. This star shaped effect is known as an asterism and is a less pure form of sapphire. All colors of the translucent form of the mineral corundum are known as sapphires. If, however, there are just the right quantities of chromium in the corundum a deep red ruby is formed... Rubies Only the red-colored forms of the mineral corundum are called rubies. All other colors are sapphires, preceded by the word "fancy" or by the special color name if they are anything other than blue. The natural crystal form of an uncut ruby is a hexagonal prism or blade (see below right). The largest ruby in the world is the Eminent Star ruby, believed to have come from India. It is 6,465 carats. Rubies are in a class by themselves.

They are the rarest of the most precious gemstones in the world and a large (5 carats or more), translucent ruby can fetch millions of dollars. Both rubies and sapphire specimens that have impurities, or have weaker colors can be enhanced by heat treating them. This helps to remove the impurities that cloud the stones and deepens their color. Heat treated-stones are not as desirable as those that are naturally translucent and deeply colored. Copyright © 1998-2015. Information about Sapphire Types Color: Most any color some stones show zoning Cleavage: is absent, although there is parting which occurs in three directions Transparency: Crystals are transparent to translucent Associated Minerals: calcite, feldspars, garnets, micas and zoisite ENHANCEMENTS: Heat treating is Common. Diffusion treatment is done occasionally. Diffusion places a thin blue coating on colorless sapphire. Irradiation is rarely used. Irradiation turns colorless gems yellow, orange or light blue. Birthstone for September: Sapphire is often considered to be synonymous with the color blue. However, sapphie comes in every color but red. Red is called ruby.

The other colors of sapphire can be just as beautiful and rare. Or even more rare than blue. Some are even considered to be collectors items. However, they are usually priced less. Yellow, orange, lavender, and other pastel shades are especially affordable. The International Colored Gemstone Association has passed a resolution that the light shades of the red hue should be included in the category ruby since it was too difficult to legislate where red ended and pink began. In practice, pink shades are now known either as pink ruby or pink sapphire. Either way, these gems are among the most beautiful of the corundum family. The ancient Persians believed that the earth rested on a giant sapphire whose reflection gave the sky its color. Damigeron, a historian of old, wrote that sapphire was worn by kings to protect them from harm. It was also believed that sapphire would protect the wearer from envy and attract divine favor. The gem was regarded as a symbol of truth, sincerity and constancy. Legend has it that if a poisonous snake were put into a vessel along with a sapphire, the rays from the gem would kill it. Our ancestors interpreted this to mean that sapphire was an antidote against poison. At one time.

Any blue gem material was called sapphire. References to a blue-flecked stone, led mineral experts to realize that some of what had been called "sappheiros" was actually lapis lazuli. "Sappheriros" is Greek for "blue." From the Mountains of Kashmir The finest sapphire color is rich, velvety cornflower blue. This is called "kashmir" out of the deference to the traditional source of the finest quality. Today, however, the Kashmir area of India is not generally mined because of its physical inaccessibility. Most current production comes from Sri Lanka, Burma, Thailand, Montana, Australia and Africa. The most valuable other fancy sapphire is a orange-pink or pinkish-orange called "padparadscha" after the lotus blossom. Padparadscha sapphires are very rare and the exact definition has always been a matter of debate: different dealers and different laboratories around the world disagree on the exact color described by this term. Some dealers even argue that the term should not be limited to the pastel shades of Sri Lankan sapphires but should also include the more firey shades of reddish-orange from the Umba Valley in Tanzania.

Star Sapphires: have fine, needle-like inclusions called asterism. When these inclusions are numerous enough to make the stone translucent or opaque and are oriented properly, they allow light to be reflected in such a way that a moving star forms across the top of the stone. When a cutter recognizes this potential in a piece of rough sapphire, he will cut it in a dome shape. Stars are not visible in faceted stones. The Sinhalese believed the star sapphire would protect them against witchcraft. The three intersecting rays were thought to represent faith, hope and destiny. Museums the world over exhibit star sapphires that are noteworthy for size or quality. The 543-carat "Star of India" resides in the Morgan-Tiffany Collection in the American Museum of Natural History in New York City. Major Deposits and Characteristic Colors: AFRICA Africa has numerous deposits of gem quality corundum and has recently been a source of new sapphire and ruby discoveries. Tanzania Umba River: Some blue, lavenders and purples to plums, yellows, golds to orange browns, pinks, and padparadschas.

Songea: Deep red rubies, blues, blue greens, greens, yellows, pinks, alexandrite-type Or color change (blue in sunlight and fluorescent light, lavender to purple in incandescent). Tunduru: Full spectrum of colors. Madagascar Blue, very much like Sri Lankan blue. The rubies are clear red and often unheated. Range of pink from pale to intense. Kenya Lodwar: - Clear deep blue to very dark blue-green and an abundance of opaque blue stars. Garbatula: deep, blackish blue-green to intense pleasant green. ASIA Sri Lanka The island nation south of India was known as Ceylon for many generations. Consequently "Ceylon-blue" is a color name outliving the change in national name. Sapphires of note in large sizes - over 5 carats - of outstanding color are predominantly of Sri Lankan origin. White, blue, purple, pink, yellow, gold, and padparadaschas. Mysore (India) Star rubies. Myanmar (Burma) Ruby and sapphire mines of Burma are legendary and have produced some of the world's finest rubies and blue sapphires.

Mogok Stone Tract Star rubies, star sapphires, rubies. Sapphire - violet, yellow, color-change, and blue. Mongshu Ruby. Thailand (Siam) Thailand is a traditional supplier of sapphire and ruby. The majority of sapphire production from the Kanchanaburi field has been mined in the last ten years. This deposit is approaching depletion. Chantaburi blue, rubies, dark blue, green, yellow, and black star - 6 and 12 ray. Kanchanaburi blue and green, yellow and rubies. Vietnam Rubies and sapphires have been found in Vietnam since the late 1980's. They are very rarely seen in the jewelry market. Luc Yen & Quy Chau: red and red-pink rubies, hot pink and purple sapphire. Cambodia: PAILIN - blue sapphire and color change ruby. AUSTRALIA: Australia also has several deposits and contributes greatly to the sapphire jewelry market in mostly Inky blues to less known brilliant true blues, green, blue-green, yellow-green, yellows, oranges, and some pinks.

NORTH AMERICA Montana is the major US source and has four main deposits. Dry Cottonwood Creek: yellow, gold and green, some pink, blue, and very, very rarely a ruby. Missouri River: green, blue, yellow, orange, pink, and very rarely ruby. Rock Creek: full spectrum of colors including many bicolors, and also very rarely ruby. Yogo Gulch: NOVA - Official Website | A Primer of Gemstones NOVA Posted 02.01.00 NOVA Diamonds, rubies, emeralds, and sapphires may reign supreme on the red carpet, but a broader spectrum of gems have captivated humans through the ages. Here, see 20 of the world's most prized gemstones, together with the properties that experts use to distinguish them from one another and from artificial look-alikes. Â Agate has a striking color banding due to slight differences in the compositions and grain sizes of the crystalline fibers.

Enlarge Photo credit: © International Colored Gemstone Association/Bart Curren Agate Agate, along with carnelian, chrysoprase, jasper, and flint, is a variety of chalcedony, a type of quartz made up of tiny crystalline fibers. Class : semiprecious Origin of Name : from the Latin achates, the former name of Sicily's river Drillo, along which agate was found in ancient times Color : green, yellow, red, reddish-brown, white, bluish-white Geographic Origins: worldwide but chiefly Brazil and Uruguay Â Amethyst's brilliant purple color has often been associated with royalty, but because of its widespread availability, the gem is a favorite among "commoners" as well. Enlarge Photo credit: © International Colored Gemstone Association/Van Rossen Amethyst Amethyst is a transparent variety of quartz that contains trace amounts of iron, an impurity that lends amethyst its lovely violet hues.

Class: semiprecious Origin of Name: possibly from the Greek amethustos ("not drunken"), perhaps given to the stone in the belief that the wearer would not suffer greatly from drinking too much alcohol Color: various shades of purple Chemical Composition: silica Geographic Origins: Brazil, Mexico, Ontario Â Aquamarine can range in color from pale to deep blue, and its color fades with prolonged exposure to sunlight or heat. Enlarge Photo credit: © International Colored Gemstone Association/Bart Curren Aquamarine Aquamarine is a variety of the mineral beryl, which also includes emerald and lesser known gems such as heliodor, goshenite, and the beautiful rose-pink morganite. Class: semiprecious Origin of Name: from the Latin aqua marina (sea water) Color: blue, blue-green, green Chemical Composition: beryllium aluminum silicate Crystal System: hexagonal Geographic Origins: Madagascar, Sri Lanka, Russia, Brazil, Colorado, North Carolina Â One of the most prized varieties of chrysoberyl is commonly called "cat's eye," for reasons obvious in this specimen.

Enlarge Photo credit: © International Colored Gemstone Association/Bart Curren Chrysoberyl Harder than all other gemstones save diamond and corundum, chrysoberyl is strongly pleochroic, meaning different colors—such as red, orange-yellow, and green—appear depending on which angle you view the gem from. Class: sometimes considered precious Origin of Name: from the Greek chrysoberyllos (golden beryl) Color: green, greenish-yellow, brown Chemical Composition: beryllium aluminum oxide Crystal System: orthorhombic Geographic Origins: Sri Lanka, India, Burma, Brazil Â The hardest substance known, diamond is prized for its exceptional luster and ability to break up white light into all colors of the rainbow, which lend the gem its famous fiery brilliance. Enlarge Photo credit: © BBC Diamond While tiny diamonds are the stuff of dental drills, large and rare specimins are the most valued of gems.

In 1995, Sotheby's sold a 100.1-carat, pear-shaped "D" flawless diamond to a Saudi Arabian sheikh for $16,548,750, the highest price to date paid for a diamond. (One carat equals one-fifth of a gram.) Class: precious Origin of Name: from the Greek adamas (unconquerable), a nod to its unequaled hardness Color: clear, yellow, brown, green, blue, pink, and rarely, red Chemical Composition: carbon Geographic Origins: South Africa, India, Indonesia, China, Russia, Australia, Brazil, California, Colorado, Canada Â Emerald gets its green color from the elements chromium and vanadium. Enlarge Photo credit: © International Colored Gemstone Association Emerald Emerald, like aquamarine, is a variety of the mineral beryl. The largest gem-quality emerald crystal, found in Colombia's Cruces Mine in 1969, weighed 7,025 carats, or about three pounds.

Class: precious Origin of Name: from a Persian word that later appeared in the Greek as smaragdos, from which the form esmeralde and later emerald were derived Color: blue-green to green Chemical Composition: beryllium aluminum silicate Crystal System: hexagonal Geographic Origins: Colombia, Zimbabwe, Zambia, Pakistan, Russia, Australia, North Carolina Â Garnet, often thought of by laypeople as a single mineral of a deep red color, occurs in many colors. Enlarge Photo credit: © International Colored Gemstone Association/Bart Curren Garnet Garnet has a number of varietal names depending on color and composition. Examples include almandite, pyrope, rhodolite, grossular, uvarovite, spessartine, andradite, and demantoid. The latter is the most expensive kind of garnet, usually more expensive than emerald.

Class: semiprecious Origin of Name: probably from Latin granatum (pomegranate), presumably for similarity in color between the gem and the fruit Color: red, orange, yellow, green, clear Chemical Composition: magnesium, iron, or calcium aluminum silicates Crystal System: cubic Geographic Origins: numerous sources worldwide Â Jade's material properties make it well suited for elaborate carvings as well as polished jewelry. Enlarge Photo credit: © International Colored Gemstone Association Jade Jade comes in two varieties: jadeite, originally found in Guatemala and carved by early Indian civilizations, and nephrite, most famously carved by the Chinese. The largest piece of jade ever found was a 636-ton lens of nephrite jade unearthed in Canada's Yukon Territory in 1992.

Class: semiprecious Origin of Name: from the Spanish piedra de hijada, name given for the jadeite carved by Indian civilizations of Central America Color: white to green, orange, brown, lilac (jadeite); green to creamy-white (nephrite) Chemical Composition: sodium aluminum silicate (jadeite), calcium magnesium aluminum silicate, with some iron (nephrite) Crystal System: monoclinic (jadeite and nephrite) Hardness: 7 (jadeite), 6.5 (nephrite) Specific Gravity: 3.3-3.36 (jadeite), 2.9-3.1 (nephrite) Geographic Origins: Burma (jadeite); Siberia, New Zealand, Taiwan, British Columbia Â The use of lapis lazuli for jewelry, vases, boxes and sacred objects dates back 6,000 years.

Enlarge Photo credit: © International Colored Gemstone Association/Bart Curren Lapis lazuli The best lapis lazuli still comes from the Sar-e-Sang mines in Afghanistan, where the vivid blue rock was traded to Egypt and Sumer (Iraq) in ancient times, and later throughout the East and Europe. Class: semiprecious Origin of Name: from the Persian lazhward (blue) Color: dark blue to greenish-blue to purple-blue Chemical Composition: aggregate of several minerals, including hauyne (which lends the stone its color), sodalite, nosean, and lazurite (a combination of hauyne and sodalite) Crystal System: the four minerals above belong to the cubic system Hardness: 5.5 Geographic Origins: Afghanistan, Siberia, Chile Â Moonstone is famous for its pearly blue opalescence and bronzy iridescent luster. Enlarge Photo credit: © International Colored Gemstone Association/Bart Curren Moonstone Moonstone is a member of the feldspars, the most abundant mineral group in the Earth's crust.

Class: semiprecious Origin of Name: named for its pearly luster, reminiscent of the Moon Color: colorless, white to yellowish grey, reddish to bluish grey Chemical Composition: potassium aluminum silicate Crystal System: monoclinic Hardness: 6 Specific Gravity: 2.56-2.59 Geographic Origins: Sri Lanka, India, Madagascar, Burma, Tanzania, Colorado, Indiana, New Mexico, New York, North Carolina, Pennsylvania, Virginia, Wisconsin Â Precious opal, as compared to common opal, offers the rainbow iridescence that has been highly prized since Roman times. Enlarge Photo credit: © International Colored Gemstone Association Opal Australia boasts the largest opals: a 26,350-carat gem-quality white opal found in 1989, and a 1,982.5-carat gem-quality uncut black opal unearthed in 1986.

(One carat equals one-fifth of a gram.) Class: sometimes considered precious Origin of Name: probably derives from the Sanskrit word upala (precious stone) Color: pale (white opal); clear (water opal); black, grey, or brown (black opal); yellow, orange, red (fire opal) Chemical Composition: silica with up to 10 percent water (in precious opal) Crystal System: non-crystalline or only poorly crystalline Hardness: 5.5-6.5 Specific Gravity: 1.98-2.20 Geographic Origins: Australia (white and black opal), Mexico (fire and water opal), Brazil, Guatemala, Honduras, Nevada, Oregon, Idaho Â The culturing of pearls has made this once rare gem ubiquitous. Enlarge Photo credit: © Dave G.

Houser/Corbis Pearl Although pearl is not an inorganic mineral but rather the organic product of oysters, it is considered by many to be a precious gem, and indeed, the pearl known as La Régente, weighing in at 302.68 grains (or a little over half an ounce), was sold in 1988 for $859,280. Class: sometimes considered precious Origin of Name: perhaps from the Latin perna, a kind of sea mussel Color: creamy white to silver-white; also yellow, pink, green, blue, black Chemical Composition: mostly calcium carbonate, with some conchiolin and water Crystal System: n/a Geographic Origins: Kashmir (India), Sri Lanka, Burma, Australia, Montana, North Carolina Â Transparent red spinels, which in the past were confused with rubies, are prized gemstones, but spinels come in other colors as well. Enlarge Photo credit: © International Colored Gemstone Association Spinel Next to ruby and the rare red diamond, spinel is the most expensive of all red gems, commanding prices as high as $2,000 per carat for stones above one carat in weight.

(One carat equals one-fifth of a gram.) Class: semiprecious Origin of Name: probably from the Latin spina (thorn) Color: red, orange, brown, green, blue, violet, clear Chemical Composition: magnesium aluminum oxide Crystal System: cubic Geographic Origins: Sri Lanka, Burma, Brazil Â For centuries, all topaz was thought to be yellow, but these blue gems are indeed topaz. Enlarge Photo credit: © International Colored Gemstone Association Topaz Today, the many colors of topaz—from classic yellow to pink—are well-known. Since 1988, the Smithsonian Institution has displayed the 22,892.5-carat (or roughly 10-pound) American Golden Topaz.

Class: sometimes considered precious Origin of Name: reputedly named after Topazius, the ancient Greek name for the Red Sea island of Zebirget (though only the gem peridot is found there); alternatively, may derive from the Sanskrit tapas (fire) Color: clear to pale blue to yellow, orange, brown, and pink Chemical Composition: aluminum fluorosilicate with some hydroxyl Crystal System: orthorhombic Geographic Origins: Brazil, Russia, Mexico, California, Colorado, Utah, Maine, New Hampshire Â Tourmalines not only come in a spectrum of colors, they can also be dichromatic—changing color when viewed from different directions.

Enlarge Photo credit: © International Colored Gemstone Association/Bart Curren Tourmaline Tourmaline shows the greatest range of colors of any gem and its varieties of composition led the Victorian thinker John Ruskin to write that "the chemistry of it is more like a medieval doctor's prescription than the making of a respectable mineral." Class: semiprecious Origin of Name: from the Sinhalese tourmali (mixed stones) Color: most colors, most popularly pink and green Chemical Composition: complex silicate of boron and aluminum Crystal System: trigonal Geographic Origins: Iran, southwestern U.S. Â Zircon, an authentic and luminous gemstone, is sometimes confused with the artificial (and often maligned) material cubic zirconia. Enlarge Photo credit: © International Colored Gemstone Association Zircon Zircon resembles diamond in its luster and fire, yet it has a tendency to chip out at the facet junctions over the years, so it not prized as highly.

(Cubic zirconia, a well-known diamond simulant, is an altered form of the mineral baddeleyite, whose chemical composition is zirconium oxide.) Class: semiprecious Origin of Name: from the word zargoon, meaning vermilion in Arabic or golden-colored in Persian Color: vermilion, yellow, green, brown, blue, clear Chemical Composition: zirconium silicate In their classic book Gemology (Wiley, 1979), the mineralogists Cornelius Hurlbut of Harvard and George Switzer of the Smithsonian Institution claim, "Since there is no rigid set of criteria that separate gems of great value from those of less value, the term semiprecious should be abandoned and all gems referred to as precious." However, since many people still divide gems between the two types, we offer here definitions of precious and semiprecious stones from The Glossary of Geology , 3rd Edition, published by the American Geological Institute: Precious stone: "A gemstone that, owing to its beauty, rarity, durability, and hardness, has the highest commercial value and traditionally has enjoyed the highest esteem since antiquity; specifically, diamond, ruby, sapphire, and emerald (and sometimes

 pearl, opal, topaz, and chrysoberyl)." Semiprecious stone: "Any gemstones other than a precious stone, or any gemstone of lower commercial value than a precious stone; specifically, a mineral that is less than 8 on the Mohs scale of hardness.

A gemstone may also be regarded as semiprecious because of its comparative abundance, inferior brilliance, or unfamiliarity to the public, or owing to the whims of fashion. This arbitrary classification is misleading, as it does not recognize, for example, that a ruby of poor quality may be far less costly than a fine specimen of jadeite." Color Gemstones gain their color from the way they affect light as it passes through them. Like a prism, a clear diamond splits incoming light into its constituent wavelengths, creating a pleasing rainbow of colors. Many other gems get their distinctive colors by absorbing one or more wavelengths, because of their chemical compositions. Rubies and sapphires, for example, are both varieties of the mineral corundum, identical in almost every respect. The difference lies in the trace amounts of other elements present. A dash of chromium makes a vivid red ruby; a bit of iron and titanium results in a deep blue sapphire. Chemical composition Gemstones have specific chemical compositions that serve to identify them. Diamond consists of carbon, for instance, while emerald is a beryllium aluminum silicate and peridot is a magnesium iron silicate. Some gemstones, such as jade, are aggregates of one or more minerals.

Crystal system All crystalline minerals consist of atoms packed in geometric arrays; the arrays, called crystal structures, are divided into seven crystal systems based on the symmetry of their atomic geometries. Mineralogists distinguish among the different crystal systems by drawing imaginary lines called crystallographic axes between the points, joints, or planes of the crystals. These lines intersect in characteristic ways at a point within the crystal called the origin. Crystals in the cubic system, for example, have three crystallographic axes, all of equal length and all at right angles to one another. (Note that cube-shaped crystals are not the only kind in the cubic system; other shapes, including octahedrons and icositetrahedrons, also qualify, because they have crystallographic axes that meet the definition.) Crystals of the cubic system: a cube (e.g., pyrite) at left, and an octahedron (e.g., diamond) at right. Note the three crystallographic axes, which meet in the center, are of equal length. Enlarge Photo credit: © WGBH Educational Foundation A second type of crystal system, known as tetragonal, also has three crystallographic axes at right angles to one another.

However, while two of the axes are of equal length, the third is either shorter or longer. The bipyramid, for example, is an elongated octahedron. Crystals of the tetragonal system: a bipyramid at left and a prism and two bipyramids (e.g., zircon) at right. Note the vertical crystallographic axis differs in length from the two horizontal axes. Enlarge Photo credit: © WGBH Educational Foundation The five other systems are hexagonal, trigonal, orthorhombic, monoclinic, and triclinic. Along with composition, crystal structure determines a mineral's properties. It also influences what happens to light when it enters a mineral and where planes of weakness may lie, which helps gemcutters. Hardness Hardness, which mineralogists can use to help identify minerals, is a measure of a gemstone's resistance to abrasion. In 1822, the Austrian mineralogist Friedrich Mohs developed the Mohs scale, a standard scale using 10 familiar minerals against which all minerals are measured. A mineral (or, on the scale below, an everyday object) will scratch all minerals of a lower number on the scale.

The intervals between minerals on the scale are not uniform, however. For instance, the difference in hardness between diamond and sapphire is much greater than that between sapphire and topaz. The minerals, from least to most hard and interspersed with several everyday objects for comparison, are as follows: talc diamond Origin of name The origins of the names of many gemstones have come down to us from antiquity and in many cases are somewhat obscure, but in those cases we offer the best guesses of historians. Specific gravity Specific gravity, a property that mineralogists use to identify minerals, is the number of times heavier a gemstone of any volume is than an equal volume of water. That is, it is the ratio of the density of the gemstone to the density of water. This feature originally appeared on the site for the NOVA program The Diamond Deception . Further Reading Ruby: The gemstone Ruby information and pictures Advertising Information The Precious Gemstone Ruby Ruby is distinguished for its bright red color, being the most famed and fabled red gemstone. Beside for its bright color, it is a most desirable gem due to its hardness , durability, luster, and rarity. Transparent rubies of large sizes are even rarer than Diamond s.

Ruby is the red variety of the mineral Corundum . Sapphire , the other gem variety of Corundum, encompasses all colors of Corundum aside from red. In essence, Ruby is a red Sapphire, since Ruby and Sapphire are identical in all properties except for color. However, because of the special allure and historical significance, Ruby has always been classified as an individual gemstone, and is never identified as a form of Sapphire (though some purplish-red colors may straddle the line of being classified as either Ruby or Sapphire). Ruby ON EBAY ALL ABOUT The color of Ruby ranges from bright red to dark reddish-brown. The most preferred color is a deep blood red with a slightly bluish hue. Such Ruby is known as " Burmese Ruby " or " Pigeon's Blood Ruby ". Ruby from Burma is famous for its exceptional coloring, and has traditionally produced the finest Rubies. However, Burmese Ruby rarely exceeds several carats; large flawless Burmese Rubies can be worth millions of dollars. Many Rubies on the market are from Thailand, and these Rubies have a less-desirable brownish hue, though they often can be heat treated to improve color.

Heat-treating a Ruby can also increase its transparency by removing tiny internal flaw s. Inclusions of tiny, slender, parallel Rutile needles in Ruby cause a polished gem to exhibit asterism . A Ruby displaying asterism is known as a " Star Ruby ", and if transparent can be very highly prized. Star Rubies exists in six ray stars, though twelve ray stars are also known. Rubies must be have good transparency to possess gem value. Opaque or semi-opaque Rubies have relatively little value, even if they display asterism . The same Rutile inclusions that are responsible for asterism in certain Rubies can also decrease transparency and cause a hazy effect known as silk. Though Ruby can be one the most expensive gemstones, it also comes in more dull opaque forms that are fairly inexpensive, and are often polished into cabochon s. A unique gemstone form composed of opaque red Ruby in contrasting green Zoisite is well known from Tanzania, and is used as a minor gemstone and can be carved into ornaments. The color of Ruby is usually caused by minute inclusion s of the metal chromium. These impurities are often responsible for causing a Ruby to fluorescent , which can be helpful in its identification.

Ruby is also pleochroic , and will sometimes display a lighter and more intense color when viewed at different angles. Ruby is a tough and durable gem, and the only natural gemstone harder than Ruby is Diamond . Despite this, Ruby is still subject to chipping and fracture if handled roughly, and care should be taken to ensure it is properly handled. Ruby was first synthesized in 1902. The process of creating synthetic Ruby is known as the Verneuil process . Only experts can distinguish between natural and synthetic, lab-created Ruby. USES Ruby is one of the most popular gemstones, and is used extensively in Jewelry. Ruby is used in all forms of jewelry, including bracelets, necklaces, rings, and earrings. It is used both as centerpiece gemstone in pendants and rings, as well as a secondary stone to complement other gemstones such as Diamond s. Star Ruby is polished as cabochon s, and, if clear, can be extremely valuable. Large Ruby gems are extremely rare and valuable. Fine colored Ruby with a deep red color and excellent transparency can reach several thousand dollars a carat . Synthetic Rubies are inexpensive and often used as a cheap substitute for natural rubies. Ruby is the birthstone for July.

Ruby TREATMENTS AND ENHANCEMENTS Rubies are often heat treated to improve color as well as burn out certain inclusion s. It is common industry practice to heat treat Rubies, and untreated Rubies with excellent natural can be exceptionally valuable. A recent practice in the gemstone industry is to fracture-fill Rubies to conceal flaw s. This is done by heating them in molten lead glass which has a very similar refractive index to Ruby gemstones. Fracture-filled Rubies are significantly cheaper than their more authentic counterparts, and because of this one should always buy Ruby from a reputable dealer. Ruby SOURCES The center of Ruby gemstone trade is in Bangkok, Thailand. The Chantaburi Province in Thailand has always been an important source of Rubies, producing gems with excellent clarity but with less desirable browner tones. However, the color of Thai Rubies are able to be improved by heat treatment . The Thai Ruby deposits were exhausted in the 1980's. The most valuable Rubies with the finest natural color come from Mogok, Burma (Myanmar). There are strict trade embargoes and restrictions again Burma for its human rights violations, and several countries, especially the United States, ban any exports from this county.

The Ruby mines of Mogok have been under the tight control of the Junta government; however, a new very significant Ruby source was discovered in Burma in 1992 in Mong Hsu. The color of these Rubies aren't as good as Mogok, but they too can be improved through heat treatment . In 2000, new Ruby sources were discovered in Madagascar (in Vatomandry and Andilamena). These deposits turned out to be very extensive and productive, and Madagascar is now one of the leaders in Ruby output. Other important Ruby sources include Sri Lanka, India, Cambodia, Vietnam, Tanzania, and Mozambique. Other sources of Ruby include Afghanistan, Pakistan, Tajikstan, Australia, and the U.S. (North Carolina). SIMILAR GEMSTONES Ruby is identical in appearance to Ruby Spinel . In fact, many old famous red gemstones thought to be Rubies were determined to actually be Spinel. Ruby and Spinel often occur together in the same mineral environment and localities. The most famous ruby, the Black Prince's Ruby, set into the royal crown of England, was once thought to be the largest cut Ruby, until scientific analysis determined it to be in fact Spinel.

Garnet (particularly Pyrope ) and red Tourmaline ( Rubellite ) may also resemble Ruby, though Ruby is significantly harder. Ruby PHOTOS [Click photos for more details] Ruby JEWELRY PHOTOS [Click photos for more details]

Question: Rubies and sapphires are varieties of which mineral?
Answer: Corundum