What is topaz streak

Subsequent exposure to light or heat will usually cause the brown portion of the color to fade leaving a blue color that is stable to light.

Additional heating will cause this blue color to fade and the topaz will become colorless once again. Some brown topazes that contain chromium impurities will become pink to violet upon heating. These colors are stable to light and this process can be reversed by subsequent irradition.

Other minerals sometimes associated with topaz in pegmatites are spodumene , lepidolite and apatite. Topaz occurs in metamorphic rocks by fluorine metasomatism in greisens and quartzites associated with fluorite , zinnwaldite , corundum and rutile. It also occurs rarely in schists.

Topaz appears in hypothermal ore deposits associated with cassiterite, hematite, wolframite and gold. The name 'topaz' was used to refer to any yellow stone in ancient times. Topaz was first used to describe the mineral that we know today as topaz in when Henckel described the Saxony deposits. Even today one often encounters the erronious terms smoky topaz and madeira topaz being used for smoky quartz and citrine quartz, respectively.

Until the 18th century, the name topaz was often used in refering to our present day mineral peridot. The name 'topaz' is thought by many to be derived from the ancient Sanskrit word tapas meaning fire. Another theory which was first put forth by Pliny in the first century A. John' which is thought to have been an ancient source for the gem peridot , but not topaz.

Popularity Prevalence Demand Pycnite - A columnar variety of Topaz. Topaz is a very popular gemstone. All colors are fashioned into gemstones, and the yellow-brown Imperial is especially valuable.

Crystals, especially those still in a matrix , are greatly sought by mineral collectors. The most important Topaz deposits are in Brazil.

Exceptionally large crystals come from many of the Brazilian pegmatite localities in Minas Gerais, especially at Itinga and Virgem da Lapa, in the Jequitinhonha valley. The famous golden orange-brown Imperial Topaz , as well as Topaz of pinkish tones, come from the famous occurrence in Minas Gerais at Ouero Prito.

Multicolored yellow and blue Topaz comes from Nerchinsk, Transbaikalia, Russia; and transparent and often etched crystals from Volodarsk-Volynskii, Zhytomyr, Ukraine. Glassy colorless and sherry crystals, some very large in size, come from the gem mines at Mogok, Burma Myanmar.

Pink and purple Topaz with exceptionally deep color comes from Katlung, Khyber, Pakistan. Classic yellow Topaz crystals once came from the Schneckenstein, Klingenthal, Saxony, Germany; and odd-shaped radiating microcrystals from the Eifel Mountains of Germany.

In the U. Fine colorless and light blue tabular crystals come from Mason Co. Other localities include the Tarryall Mts, Park Co. Quartz especially Citrine - Slightly softer 7 , lacks cleavage , forms in different crystal habits. Chrysoberyl - Lacks cleavage, different crystal habits. Beryl - Lacks cleavage, crystallizes hexagonally. Apatite - Much softer 5 , different crystals. Danburite - Slightly softer 7 Fluorite - Much softer 4 , different crystals.

Barite - Forms in similar crystals but is much softer 3. 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. 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. 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 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, Another significant topaz sample is the Topaz of Aurungzebe; this gem was documented by Jean Baptiste Tavernier as measuring some Certainly a gemstone over carats is significant but in comparison to the amazing 22, 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. 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 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. This generic reference does not take in to account anything but the actual color of the gemstone in question. 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.

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.

The Strunz classification is a system that was introduced by the German mineralogist Karl Hugo Strunz in 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.