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What Are Mineraloids?
A mineraloid is a naturally occurring, inorganic solid that does not exhibit crystallinity. It may have the outward appearance of a mineral, but it does not have the “ordered atomic structure” required to meet the definition of a mineral. Some mineraloids also lack the “definite chemical composition” required to be a mineral. To be considered a…
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Minerals in the Sedimentary Cover
Both the oceanic and continental crusts are partly covered with a thin layer of sedimentary rocks and sediments. These consist mainly of clastic rocks such as sandstone, siltstone and shale, along with carbonate rocks such as dolostone and limestone. These clastic rocks are composed of mainly quartz, clay minerals, and a small amount of micas and feldspar minerals. The carbonate…
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Minerals of the Continental Crust
As a second example, let’s consider the rocks of the continental crust. The continental crust is made up mainly of rocks with a granitic to andesitic composition. These rocks are composed mainly of alkali feldspar, quartz, and plagioclase feldspar, with smaller amounts of amphiboles and micas. This small number of minerals makes up most of the continental crust.
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Minerals of the Oceanic Crust
As an example of the influence of just a few minerals, let’s consider the rocks of the oceanic crust. The oceanic crust is mainly composed of basalt and gabbro. These two rock types are made up of mainly of plagioclase feldspar and pyroxenes, with smaller amounts of olivine, micas and amphiboles. This small group of minerals makes up most of…
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What Are Rock-Forming Minerals?
Scientists have identified over 4,000 different minerals. A small group of these minerals make up almost 90% of the rocks of Earth’s crust. These minerals are known as the common rock-forming minerals. To be considered a common rock-forming mineral, a mineral must: A) be one of the most abundant minerals in Earth’s crust; B) be one of the original minerals present at…
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Zircon and Radioactive Decay
Many zircon crystals contains trace amounts of uranium and thorium. These radioactive elements were incorporated into the zircon at the time of crystallization. They convert into their decay products at a steady rate. The ratio of parent materials to daughter products can be used to estimate the time of crystallization. Using this method, the oldest…
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Industrial Uses of zircon
Zircon sand has a low expansion coefficient and is very stable at high temperatures. It is used as a refractory material in many foundry and casting applications. One of its most common uses is in the production of ceramics. Zirconium dioxide (zirconia) is produced by heating zircon sand to a high enough temperature to break…
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Zircon, Zirconium, Zirconia, CZ
There is much public confusion between four materials: zircon, zirconium, zirconia and cubic zirconia. Summary definitions of these terms are provided below. Zircon is a naturally occurring mineral with a chemical composition of ZrSiO4. Zirconium is a silvery white metal and a chemical element. It has an atomic number of 40 and an atomic symbol of Zr.…
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Zircon Mining
Zircon has been mined from stream gravels for over 2000 years. This early mining of zircon was mainly to obtain nice crystals for use as gemstones. Today, most zircon is produced by mining or dredging zircon-rich sediments. These sediments can be in beach, littoral, or alluvial deposits. Zircon has a specific gravity of 4.6 to…
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Zircon in Tanning and Nail Salons
Most blue zircon sold in jewelry today is produced by heat treating brown zircon in a reducing atmosphere to 900 to 1000 degrees Celsius. Some people have damaged these blue zircons by exposing them to ultraviolet radiation in tanning beds or under ultraviolet lamps used to cure acrylic fingernail adhesives. The blue color can degrade…