Mineral Albite
The chemical composition of the mineral Albite is indicated by NaAlSi3 O8, Sodium Aluminum Silicate. This mineral belongs to the Silicates mineral class. Albite mineral is also known as a member of the feldspars. It is also considered as a pivot mineral of two different feldspar series. It is often associated with the plagioclase series and Albite is known to be the end member of this feldspar series. Plagioclase feldspar minerals can be easily distinguished from each other thru their respective indices of refraction and specific gravities without any further chemical analysis and/or optical measurements made. This mineral Albite is also known as an end member of the Alkali or the K-feldspar series. At high temperatures, this series exist with their Potassium rich end member called Sanidine. In the process called exsolution, the K-feldspar minerals will separate from the Albite mineral in low temperature and thus Albite forms crystal layers within the K-feldspar mineral. The stone formed in this process is known as perthite. The crystal layers of the mineral Albite within the K-feldspar mineral is visible by the naked eye and much splendidly visible in transmitted light of a petrographic polarizing microscope. The cation position in crystal structure must contain not less than 90% sodium and not more than 10% potassium and/or calcium. This mineral Albite is used in the manufacturing of glass and ceramics aside from being a rock-forming mineral.
The name of the mineral Albite comes from the Latin word “albus”, meaning white. This is an allusion to the white color commonly exhibited by the mineral in both reflected and transmitted light of polarizing microscopes. Feldspar is derived from the German word “feld” which means field. Its first reported occurrence in Sweden was in the year 1815.
Mineral Albite has a triclinic crystal system that includes blocky crystal habits. They also sometimes exhibit tabular and platy habits when viewed in reflected light in polarized light microscopy. Crystals are sometimes showing rectangular or square cross-sections with slightly slanted dome and terminated by pinacoid faces, which can be found clearly exhibited when the mineral is viewed reflected light of a petrographic polarizing microscope. By minor adjustment on the aperture diaphragm of polarized light microscope, a low relief is found. By the appearance of possible surface relief, cleavage can also be possibly found. Mineral Albite has perfect cleavage found in one direction and good in the other direction, forming nearly right angled prisms. Cleavage usually intersects at 93? – 94?. Fracture is commonly found conchoidal in reflected light of petrographic polarizing microscope. Mohs scale hardness ranges from 6 – 6.5 giving 6.25 average. Specific gravity is approximately 2.61 g/cm³ in average. Albite shows white streak when rubbed on a white streak plate. It also shows vitreous luster in reflected light of a polarizing light microscopes. They may exhibit dull luster if they appear to be weathered. Most common crystal appearance is variations of translucent to opaque and may appear rarely transparent.
Indices of refraction found in crossed nicols of polarized microscopes also increase as trace amounts of anorthite mineral increases. Maximum interference colors exhibited are of first-order shades of white or gray. Index of refraction is normally 1.53. First-order yellow colors are only exhibited by calcic plagioclase even when viewed in polarized light of petrographic polarizing microscope. Normally, ore specimens may appear in white or gray color in ordinary transmitted light in polarized light microscopy, but sometimes may also appear in pink, yellow, or black. They may also appear colorless, where all constituents of the ordinary transmitted light of polarized microscope can pass through. But it can also exhibit shades of blue, orange, or brown. Albeit often shows crystal twinning as minute parallel striations on the crystal face often found when viewed under petrographic polarizing microscope.
The mineral Albite exhibits polysynthetic twinning and almost universal. The twinning appearing between crossed nicols in polarized light microscopy is series of dark and light bands, bounded by parallel edges. They are also members of the amorphous group of minerals. This mineral Albeit can be distinguished from other orthoclase members by its lamellar twinning found in crossed nicols of polarized light microscopes.
Albite is known to have the capability to crystallize in molten rocks. Being the last feldspar to crystallize in molten rocks, they are commonly isolated and naturally well-formed rare elements. The by-products therefore are those that are considered rare mineral species. Albeit mineral is commonly found hosted by other lovely rare minerals that exhibit a splendid view under an ore polarizing microscope. The Albite mineral commonly occurs in pegmatites and felsic igneous rocks like granites. There is also a possibility that they can be found in some sedimentary rocks. They may also be found in low-grade metamorphic rocks.
