. Bulletin - New York State Museum. Science. NEW YORK STATE MUSEUM Orthoclase (potash feldspar) KAlSi,Os Orthoclase is a silicate of aluminium and potassium. Part of the potassium is often replaced by sodium giving rise to a variety known as soda-orthoclase. The crystals of orthoclase are monoclinic, a type of frequent occurrence being that shown in fig. 204. Types of prismatic. Fig. 204 Orthoclase habit, often orthorhombic in aspect from the equal development of the basal pinacoid and positive hemiorthodome (fig. 205), are often found in the transparent variety called adularia. Twin crystals
. Bulletin - New York State Museum. Science. NEW YORK STATE MUSEUM Orthoclase (potash feldspar) KAlSi,Os Orthoclase is a silicate of aluminium and potassium. Part of the potassium is often replaced by sodium giving rise to a variety known as soda-orthoclase. The crystals of orthoclase are monoclinic, a type of frequent occurrence being that shown in fig. 204. Types of prismatic. Fig. 204 Orthoclase habit, often orthorhombic in aspect from the equal development of the basal pinacoid and positive hemiorthodome (fig. 205), are often found in the transparent variety called adularia. Twin crystals occur quite frequently and are ordinarily of three types, the Carlsbad, the Baveno and the Manebach The cleavage of orthoclase takes place in two directions parallel to the basal and clinopinacoid and at an angle which is close to 90°. Gleavable masses are quite common. Also compact non- cleavable masses resembling flint. The luster of orthoclase is vitreous or pearly and the color is commonly flesh-red, yellowish, white or colorless; more rarely gray or green. Orthoclase abounds in igneous rocks and constitutes an important element in granite, gneiss and syenite and in the form of sanidine is common in the volcanic rocks rhyolite, trachyte and phonolite. It is quarried in Maine, Connecticut, Massachu- setts and Pennsylvania and at Bedford and Fort Ann N. Y. Orthoclase is used in the manufacture of porcelain and china, as a constituent of the body of the ware and also to produce the glaze. 1 These forms of twinning are illustrated by specimens and models in the collection of the New York state Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original New York State Museum; New York State Museum. Albany : New York State Education Dept
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectscience, bookyear1887
