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Use of Serpentine: Gemstones
Attractive serpentine can be cut into a wide variety of gemstones. It is most often cut into cabochons and beads. They usually display a range of green, yellow, and black colors and often have magnetite, chromite, or other minerals as interesting inclusions. The lower left side of the green and black cabochon in the center of the photo…
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Use of Serpentine: Asbestos
Some varieties of serpentine have a fibrous habit. These fibers resist the transfer of heat, do not burn, and serve as excellent insulators. The serpentine mineral chrysotile is common, found in many parts of the world, is easily mined, and can be processed to recover the heat-resistant fibers. The use of chrysotile and other serpentine minerals…
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Use of Serpentine: Architectural Material
Serpentine has been used as an architectural stone for thousands of years. It is available in a wide variety of green and greenish colors, often has an attractive pattern, works easily, and polishes to a nice luster. It has a Mohs hardness of 3 to 6 which is softer than granite, and usually harder than most marble. This low…
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Physical Properties of Serpentine
The most obvious physical properties of serpentine are its green color, patterned appearance, and slippery feel. These remind the observer of a snake and that is where the name “serpentine” was derived. Serpentine is also known for its translucent diaphaneity, waxy luster, ease of being cut into shapes, and its ability to accept a polish. These…
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Serpentinites and Serpentine Formation
Serpentine minerals form where peridotite, dunite, and other ultramafic rocks undergo hydrothermal metamorphism. Ultramafic rocks are rare at Earth’s surface but are abundant at the oceanic moho, the boundary between the base of the oceanic crust and the upper mantle. They are metamorphosed at convergent plate boundaries where an oceanic plate is pushed down into the mantle. This is…
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What is Serpentine?
Serpentine is not the name of a single mineral. Instead it is a name used for a large group of minerals that fit this generalized formula:(X)2-3(Y)2O5(OH)4. In this formula, X will be one of the following metals: magnesium, iron, nickel, aluminum, zinc, or manganese; and, Y will be silicon, aluminum, or iron. The appropriate generalized formula is therefore as follows:(Mg,Fe,Ni,…
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Synthetic Rutile
Rutile has a very high refractive index, a strong dispersion, and an adamantine luster. These are optical properties that can produce a great gemstone, and these properties in rutile rival or exceed those of diamond. Unfortunately, natural rutile rarely has the clarity and color needed to serve as an alternative gem for diamond. However, synthetic rutile can…
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Uses of Rutile
The primary uses of rutile and titanium oxide made from rutile are: manufacturing titanium oxide pigments, manufacturing refractory ceramics, and production of titanium metal. The use of rutile to make pigments touches the lives of almost every person in the United States in many ways almost every day. When finely crushed and processed to remove…
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Rutile and Gemology
More than perhaps any other mineral, rutile has an affinity for growing as prism-shaped crystals within other minerals. Long prisms of rutile occur in many different gem minerals. Quartz, corundum (ruby and sapphire), garnet, and andalusite are some of the more familiar. Sometimes these needles are coarse and clearly visible within the gem, as in many specimens of rutilated quartz. These…
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Polymorphs and Impurities
Rutile is the most abundant natural form of TiO2. There are numerous polymorphs that include anatase and brookite. Iron (Fe+2) sometimes substitutes for titanium in some specimens of rutile. When this occurs, a valence difference between iron and titanium requires balancing – and that balance is often accomplished by substitution of niobium (Nb+5) and/or tantalum…