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The chemical formula of mineral Analcime is indicated by NaAlSi2O6-H2O or Hydrated Sodium Aluminum Silicate. Analcime is actually a Silicate mineral. Its name originated from the Greek word an alkimos, which means not strong. This is relative to its weak pyroelectricity. An interesting mineral known as Analcime is very popular. It has a unique crystal formation characteristic. This Analcime mineral is known to have distant relation to a mineral known as Leucite. This Leucite mineral is one member of the feldspathoid group, possessing chemical properties quite similar to that of the Alkali feldspar, with distinguishing factor of having poor silica content. Feldspathoids have common occurrence in igneous rocks having poor silica content. Analcime can be possibly found with feldspathoid in the igneous rocks of said characteristic. Due to Analcimes similar chemistry and possible occurrence with the feldspathoids, they are considered member of the said group. The structure of the Analcime mineral is known to be a typical Zeolite. It possesses this Zeolite property of being open to allow large ions and molecules to reside within them, and have their freedom to move around inside the overall framework of the mineral. It has structurally large open channels provided for the in and out of water and other large ions in the crystal framework. Sizes of the ions are controlled by the size of the open channels making the mineral Analcime a chemical sieve Zeolite.

 

            Analcime exhibits colors of white or gray and they may sometimes show tints of green, yellow, or red when evaluated with the aid of petrographic polarizing microscopes used in the field of optical mineralogy. It usually shows vitreous luster in reflected light of polarizing light microscopes for mineralogists. When mineral Analcime is evaluated under minor adjustments on the aperture diaphragm of polarized microscope in optical mineralogy, uneven or conchoidal fracture can be exhibited. The hardness measure of the mineral Analcime when evaluated using the Mohs scale method is usually ranging from 5 to 5.5 giving an average of 5.25. The specific gravity measure of mineral Analcime is approximately 3.2 grams per cubic centimeters at an average. Analcime commonly leaves a white streak when the mineral is rubbed on a white porcelain streak plate.

 

            Analcime crystal may appear transparent and sometimes translucent. When viewed under a petrographic polarizing microscope, mineral Analcime commonly shows isometric crystal structure with inclusions of trapezohedron form. In the field of 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. There may also be rare cube inclusions modified by trapezohedral faces that can be seen clearly visible when viewed with the aid of petrographic polarizing microscope used in the field of optical mineralogy. In thin sections, they usually yield from eight-sided sections to nearly round. They may appear in granular and sometimes massive crystal formations displaying splendid images under polarizing microscopes for mineralogists. The good crystals displayed by Analcime mineral are usually loose and are commonly attacted to other minerals in volcanic cavities. These minerals usually have weak birefringence when viewed in plane-polarized light of petrographic polarizing light microscopes used in the field of optical mineralogy. They may also display lower first-order interference colors when evaluated between crossed nicols of polarized light microscope for mineralogists.

 

            Analcime is known as the only Zeolite that is considered a primary mineral in igneous rocks. It is commonly found in altered volcanic zones, in vesicles, veins, in lacustrine and deep marine sediments, and other voids in basaltic rocks. It can also be found in Alkalic intrusive and extrusive units, usually in groundmass.



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Monday, November 30th, 2009 at 4:33 am
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The Silicates Mineral Class
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