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The chemical formula of mineral Cristobalite is indicated by SiO2 or Silicon Dioxide. Cristobalite is actually a Silicate mineral. The name Cristobalite was derived from the name of one of its types of locality in Cerro San Cristobal, Mexico. This mineral was actually first described and first discovered in the year 1887 at Hidalgo in Mexico. Cristobalite is known to crystallize in the tetragonal system of crystal formation. In optical mineralogy, this tetragonal system comprises crystals having three axes, which are all in a position perpendicular to one another. Two axes are usually found having the same or equal length. Beta Cristobalite on the other hand is known to crystallize in the isometric system of crystal formation. In optical mineralogy, this isometric system comprises crystals having three axes, all of which are perpendicular to one another and all are found equal in lengths. Cristobalite is actually used as an indicator of high temperature of crystallization. It is also commonly used as a mineral specimen, which usually exhibits a nice and wonderful image under polarizing light microscopes. Mineral Cristobalite is also a know polymorph of quartz. In optical mineralogy, polymorph means that the two minerals have the same chemistry but they have different structure when viewed under geological polarizing microscopes. Both quartz and Cristobalite are polymorph minerals with all the members of the Quartz Group of minerals with members including stishovite, coesite and tridymite.

 

At high temperatures, it has been known that mineral Cristobalite is called Beta Cristobalite. And most mineralogists believed that most Cristobalite minerals crystallized first as Beta Cristobalite and after cooling down would turn into Alpha Cristobalite or simply Cristobalite. The Beta Cristobalite has an isometric symmetry and the typical Beta Cristobalite crystals are usually octahedrons, which can be seen clearly when viewed with the aid of geological polarizing light microscopes. Beta Cristobalite mineral is so easily converted into Cristobalite and the isometric crystals of Beta Cristobalite are usually outwardly preserved in their original form. The higher symmetry of Beta Cristobalite is very far incomparable to the tetragonal symmetry of mineral Cristobalite. With the aid of petrographic polarizing microscope, Cristobalite crystals are usually found interior structure that is no longer isometric. Thus, it can be noticed that the octahedral looking crystals of Cristobalite that can be made visible with the aid of polarizing microscopes for geologists are actually the false shapes or the pseudomorphs.

 

            Mineral Cristobalite is most commonly found colorless or white in thin sections when mineral is closely evaluated with the aid of petrographic polarizing light microscope used in optical mineralogy. Cristobalite also exhibits high vitreous luster in reflected light of polarizing microscopes for mineralogists. Cristobalite is also most commonly found showing absent cleavage even if they are evaluated under several adjustments on the aperture diaphragm of polarized light microscopes for mineralogists. Cristobalite is also most commonly found showing conchoidal fracture when it is evaluated between crossed nicols of polarizing microscopes for mineralogists. . The specific gravity measure of mineral Cristobalite is commonly 2.32+ grams per cubic centimeters, which is commonly considered below average for translucent minerals. The hardness measure of mineral Cristobalite when it is evaluated using the Mohs scale method is commonly 6.5. Cristobalite is most commonly found leaving a clear streak when specimens are rubbed on a white porcelain streak plate

 

            Most Cristobalite mineral crystals are commonly found transparent to translucent in appearance. The crystal habit of mineral Cristobalite as described in optical mineralogy commonly includes as always the small or microscopic crystals that are usually showing nice and interesting images when viewed under polarized light microscopes used in optical mineralogy. Cristobalite minerals are also rarely found forming well-formed crystals, which are considered pseudo isometric as pseudomorphs of mineral Beta Cristobalite. Typical crystals of Cristobalite are usually pseudo octahedrons, which are usually clearly exhibited under polarizing microscopes for mineralogists. Some Cristobalite crystals are twinned in a special twin called spinel twin, which can be seen fascinatingly clear when viewed under petrographic polarizing microscopes. Most commonly, Cristobalite mineral crystals are found in radiating clusters and spherical aggregates that are very interesting and fascinating when viewed with the aid of polarizing light microscopes used in optical mineralogy. The refractive index of mineral Cristobalite when it is evaluated in plane-polarized light of polarizing light microscope for mineralogists is approximately 1.48. There are several interesting crystal formations formed by mineral Cristobalite. One of these is the white snowflake of the Snowflake Obsidian. This crystal form is actually tiny cluster of white Cristobalite crystals that form beautiful and splendid image under petrographic polarizing microscope used in optical mineralogy. Cristobalite crystals are commonly found exhibiting a strong double refraction when evaluate in plane polarized light of polarizing microscopes. Some mineral specimens of Cristobalite are fluorescent in ultra violet light.

 

            Cristobalite minerals are commonly associated with several other interesting minerals such as hornblende, augite, tridymite, olivine, sanadine, pseudobrookite and beta quartz. Mineral Cristobalite is commonly found volcanic rocks. With the aid of petrographic polarizing light microscopes, many Cristobalite crystals can be easily seen and are mostly exhibiting splendid microscope images. Larger Cristobalite crystals that are usually well formed are usually rare in occurrence. Good Cristobalite specimens can be found in the crevices and cavities called vesicles of hosting rocks. Mineral Cristobalite would be considered widely distributed in a certain type of rocks if these rocks are at the least commonly found occurring in nature. However, good macroscopic Cristobalite crystals as mineral specimens are very hard to find. Mineral Cristobalite is actually not necessarily easy to identify. But some few distinguishing factors of mineral Cristobalite can be also considered upon identification. Mineral Cristobalite are actually so common in volcanic rocks and upon evaluation of the mineral with the aid of polarizing microscopes for geologists, color and crystal habit of Cristobalite are usually sufficient basis. Another point of consideration is the index of refraction of mineral Cristobalite as well as its environment of formation. Mineral Cristobalite notably occurs at some types of localities including Cerro San Cristobal in Pachuca Mexico, Italy, Mt. Lassen in California, USA as well as the San Juan Mountains and Yellowstone National Park in Colorado, USA.



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Thursday, January 29th, 2009 at 4:05 am
Category:
The Silicates Mineral Class
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