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The most common traditional birthstone for those born in the month of November is topaz. Topaz is a silicate mineral that comes in a variety of colors and makes beautiful jewelry pieces. In this article we will discuss everything you ever wanted to know about this November birthstone including: geographical location, variety of color shades, natural formation, chemical composition and the history of this brilliant stone.
What is Topaz?
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Topaz is referred to by geologists as a silicate mineral simply because of its chemical composition. The chemical formula for this November birthstone is Al2SiO4(F,OH)2. Contained within the chemical makeup of this silicate gemstone are aluminum and fluorine. A vast number of minerals are also recognized as being “aluminum minerals” like topaz, these include: ruby, beryl, emerald and jadeite. Each of these emeralds has aluminum within their chemical composition. Unknown to many, the topaz is naturally a clear stone; however, as impurities creep in to the crystal as it forms various colors tint the final product.
The Color of Topaz
As mentioned above it is the elements that build up within the stone that cause topaz to have a particular color. Depending upon which elements build up within the stone as well as just how much of those elements are present, the color of topaz will vary. Most commonly topaz is found to be: clear, reddish-yellow, gold, blue, pink, white, gold, white, blue-brown and pale green. Some of these colors are a much rarer find than others. Some types of topaz have also gained their own names.
Imperial topaz can be a number of colors including pink, pink-orange or yellow. Imperial topaz from Brazil is often found to have a bright yellow coloration that can border on gold or violet. Occasionally brown topaz will be treated in order to give it this bright gold or violet color that is much desired. Unfortunately for their owners, some imperial topaz can lose its color when it is exposed to long periods of sunlight.
Orange topaz is most commonly referred to as “precious topaz.” This variety of topaz is the one most recognized as being the birthstone for the month of November. In addition to being recognized as the official November birthstone, the orange topaz is also recognized by many as being a symbol of friendship and the state gemstone for Utah.
Blue topaz is a fairly rare occurrence as a naturally occurring variety of topaz. Most commonly blue topaz is created through manmade processes. Blue topaz is often treated with a colorless, pale yellow, gray or blue elements are treated with heat as well as irradiated in order to create a much darker blue color. The blue topaz is recognized as the official state gemstone of the state of Texas.
Mystic topaz is a clear and colorless type of topaz that has been coated in a man-made process. The coating that is applied to this clear stone causes it to have a rainbow type appearance. This type of topaz does not appear naturally.
Where is Topaz Found?
Due to its natural composition the topaz is most often found in areas rich in granite and rhyolite deposits. These areas are most often found where rhyolite lava is commonly found or where granitic pegmatites occur. One of the richest areas of topaz deposits is the Topaz Mountain of western Utah. In addition to being found in areas of rhyolite and pegmatite, topaz is also frequently found in areas with cassiterite and fluorite. One such area is the Ural and the LLmen mountains of Russia. Topaz is also very frequently found in the United States, Australia, Nigeria, Pakistan, Sweden, Italy, Brazil, Japan, Flinders Island, Sri Lanka, Czech Republic, Norway, Afghanistan and Mexico.
The Size of Topaz Gemstones
Topaz gemstones are varied in size depending upon the type of stone. Brazilian pegmatite clear topaz crystals have been known to weigh in at hundreds of pounds and can reach the size of boulders! Occasionally these huge topaz samples can be found in museum collections because of their sheer size. One of the largest topaz found to date is the American Golden topaz that measured in at an incredible 22,892.5 carats! Another significant topaz sample is the Topaz of Aurungzebe; this gem was documented by Jean Baptiste Tavernier as measuring some 157.75 carats. Certainly a gemstone over 100 carats is significant but in comparison to the amazing 22,892.5 carats, 100 carats pales in comparison!
The Name “Topaz”
The name “topaz” has a number of potential roots, Most people believe that “topaz” comes from the old French word Topace derived from the Latin word Topazus. This word comes from the Greek work Topazios or Topazion, a name utilized to refer to the St. John Island located within the Red Sea. This island proved particularly difficult to find but once it was located a yellow stone similar to the topaz but actually understood now to be Chrysolite or yellow olivine, was mined. At the time of its discovery the gemstone topaz was not officially identified. This concept is repeated in the legend that says Pliny the elder identified the first mining of topaz on the legendary Red Sea Island.
Alternately, other individuals believe that the word topaz comes from the Arabic word that translates to mean “the subject of the search.” Others still believe that the word topaz derives from the Sanskrit word tapas that translates to mean fire or heat.
There are many potential origins for the name “topaz” and while most seem to carry some credibility the most often repeated is that of the island in the Red Sea where the brilliant yellow gemstone was discovered.
Early References to the Topaz
There are a number of early references to the topaz gemstone throughout history; however, it should be noted that at least during the middle ages the term “topaz” Was used to refer directly to any yellow tinted gemstone. Before the Middle Ages however, mention of the topaz gemstone was made in the Bible, at least according to many of the modern translations of the holy book. Just one of these mentions of topaz in the Bible is said to be found in the book of Exodus 28:17. It is important to note however, that the mention of the word topaz does not necessarily refer strictly to the topaz stone itself. As seen before, the term topaz has been used to refer to any number of yellow gemstones, most predominantly Chrysolite. Since the translations of the Bible and the broad use of the word “topaz” tend to cloud the waters, it cannot be said for certain whether or not the topaz referred to here is the same gemstone we study today under the same name.
The Generic Reference to Topaz versus the Modern Gemstone Topaz
As mentioned above the term “topaz” is often used in reference to any gemstone that has a yellow color when it is utilized in historical texts. This generic reference does not take in to account anything but the actual color of the gemstone in question. Conversely, the more modern translation of the word “topaz” is used to identify gemstones that have a composition based on silicate. Hundreds and thousands of years ago when historical reference texts were written there was no way for researchers to determine the chemical composition of any gemstone and as such, a stone would commonly be determined based upon color, appearance and untested theory.
The Scientific Classification of Topaz
It has already been mentioned that many times the gem topaz has been confused with other gems simply due to color similarities. In the modern-day however, there are many scientific measurements that can be used to identify topaz. Scientists must rely upon various pieces of data in order to classify gemstones, this data includes: Strunz classification, crystal symmetry, crystal habit, cleavage, fracture, Mohs scale value, luster, streak, diaphaneity, specific gravity, refractive index, birefringence, pleochroism and fluorescence.
Strunz Classification of Topaz
The Strunz classification is a system that was introduced by the German mineralogist Karl Hugo Strunz in 1941. This scale categorizes individual minerals based upon the chemicals that each mineral is made up of. Strunz originally came up with the scale when working with the Mineralogical Museum of Friedrich Willhelms Universitat. In need of a way to categorize the collection based upon the crystal-chemical properties of each stone he came up with the original Strunz classification. Over the years the classification system has been changed. Currently the Strunz classification system divides minerals in to ten categories including: elements, sulfides and sulfosalts, halides, oxides hydroxides and arsenites, carbonates and nitrates, borates, sulfates chromates molybdates and tungstates, phosphates arsenates and vanadates, silicates and organic compounds. The Strunz category of Topaz is silicates and as such it is assigned the number 9 since this is the ninth class. The full Strunz classification number of Topaz is 9.AF.35. This not only identifies the element as being a silicate but also identifies other mineral properties that make Topaz unique.
The Crystal Symmetry of Topaz
The crystal symmetry of a gemstone is the term used to identify the way in which symmetry appears in space groups, plane groups and point groups within the crystalline structure. The crystal symmetry of topaz is recognized as being orthorhombic dipyramidal.
The Crystal Habit of Topaz
The crystal habit of a gemstone is the term used to describe the external shape that a mineral takes when it develops naturally. The term is most often used to describe a single crystal; however, it can also be used when referring to a group of crystals as they naturally develop. The crystal habit of topaz is referred to as being prismatic crystals with faces that are striated parallel to the long dimension of the crystal. Topaz crystals are also referred to as being columnar in structure, compact and, as mentioned previously, massive.
The Cleavage of Topaz
The term cleavage when used in reference to a gemstone is used to identify the tendency of a mineral as it splits to split along definite crystallographic structural planes. The cleavage of the topaz is recognized as bring perfect and basal. Basal cleavage is also referred to as pinacoidal cleavage and can be seen in a number of mica and graphite stones. Often these crystals are rhombohedral or hexagonal in shape.
The Fracture of Topaz
When used in reference to gemstones and minerals, the term fracture refers to the texture and shape of the surface that is created when the mineral in question is fractured. There are many terms utilized to describe specific surface and textures of a mineral but the term used in reference to topaz is subchonchoidal. Subconchoidal refers to the tendency of the surface of a topaz gem to curve slightly when fractured. Subchonchoidal should not be confused with conchoidal which is a greater curve that is observed in flint, opal and quartz.
The Mohs scale Value of Topaz
The Mohs scale is used to refer to the hardness of a particular element. Elements that are particularly hard rate at a 10 on the Mohs scale and resist scratching, the perfect example of this type of element is diamond. The much softer elements such as talc do not resist scratching at all and are easily marked. The Mohs value or topaz is 8. As an 8 the topaz is a particularly hard gemstone ranking above quartz, fluorite and gypsum. Topaz is not however, as hard as corundum or diamond.
The Luster of Topaz
The term luster when used in reference to a gemstone is used to describe how the light plays on the surface of a particular gem or mineral. Topaz is referred to as being vitreous in luster. The term vitreous when used in reference to the luster of a gem means that gem has a glasslike appearance. A vitreous luster is the most popular luster seen in gemstones and can also be found in quartz, calcite, tourmaline, fluorite and beryl.
The Streak of Topaz
When used in terms of geology and mineralogy the term “streak” refers to the powder residue that remains when the mineral stone is dragged across an unweathered surface. The color of this “streak” is not necessarily the same color as the gemstone itself. In the case of topaz, the color of the streak is white.
The Diaphaneity of Topaz
The diaphaneity of a gemstone is the property of allowing light to pass through the stone. As light passes through a particular mineral it can interact with that mineral creating different colors. In the case of topaz the diaphaneity of the mineral is referred to as transparent in that it allows light to pass directly through it.
The Specific Gravity of Topaz
The term specific gravity is used to refer to the ratio of the density of a substance in reference to that same density of a reference substance. In most cases this reference substance is water. The specific gravity of topaz is 3.49–3.57. This number means that a specified amount of topaz is 3.49–3.57 times more dense than the same specified amount of water.
The Refractive Index of Topaz
When used in terms of mineralogy the term “refractive index” is used to refer to the speed at which light passes through a substance in comparison to the speed at which light passes through a vacuum. The refractive index of topaz is nα = 1.606–1.629, nβ = 1.609–1.631,nγ = 1.616–1.638. This means that depending upon the wavelength of light rays used that light passes through a vacuum anywhere from 1.606 to 1.638 times faster than it does through topaz.
The Birefringence of Topaz
The birefringence of a mineral refers to the process of a light ray decomposing in to two rays as it passes through that mineral. The birefringence value of topaz is 0.010 which is the value equal to the distance between the high and low refractive indexes of the gemstone.
Pleochroism of Topaz
Pleochroism is a term utilized to refer to the appearance of the grains within a mineral to change colors when it is viewed at different angles under polarized transmitted light under a polarizing petrographic microscope. Pleochroism of topaz is particularly weak in thick sections of the gem. Additionally pleochroism values for topaz are as follows: X = yellow, Y = yellow, violet and reddish and Z= violet, bluish, pink and yellow.
Fluorescence is a term in mineralogy that is used to refer to the ability of a gemstone to fluoresce under different wavelengths of light. Not all gemstones fluoresce. The topaz fluoresces both under short UV and long UV wavelengths. Under short UV light topaz fluoresces a golden-yellow color. Under long UV light topaz fluoresces a cream color.
Uses of Topaz
Topaz is quite a common gemstone and it comes in such a wide variety of colors and cuts that it has many uses in terms of jewelry. Most people utilize these stones as gems in jewelry pieces such as rings, bracelets, necklaces and hair berets. In addition to being used and sold commercially as jewelry, topaz is also a major collectible and is in high demand in particular forms by collectors. Most commonly yellow-brown imperial topaz is sought by collectors in addition to topaz that is still in a matrix. When referring to a mineral that is still in a matrix, collectors are talking about minerals that have a crystal emerging from them.
Distinguishing Topaz from Similar Minerals
As mentioned above, many of the characteristics above are used to identify minerals from each other. There are many characteristics to pass through when looking at similar minerals however, but there are some tips and tricks to determining topaz from commonly confused elements. Quartz is a softer gemstone that does not have cleavage, additionally it is found in different crystal habits. Beryl crystallizes hexagonally and also lacks cleavage. Fluorite is significantly softer and forms different crystals. Euclase has different cleavage characteristics. It is important to be able to make these fast distinctions between these similar gems in order to save time in a laboratory setting. It may not be as significant for the layman to be able to identify one gem from another but it certainly shows an education in gemstone identification!Tagged With: Birthstones