Minerals in rock sections; the practical methods of identifying minerals in rock sections with the microscope, especially arranged for students in technical and scientific schools . olite parallel to the base. Also yellow color is common in epidote but rare in pyroxene. Remarks : Next to the feldspars pyroxene is the most common constituent of theigneous rocks. Diopside and fassaite (green) are found in contact rocks; also, whatappear to be the same pyroxenes, in many eruptive rocks, as andesites, monzonites, (light green) is found in amphibolites and eclogites (where it may be
Minerals in rock sections; the practical methods of identifying minerals in rock sections with the microscope, especially arranged for students in technical and scientific schools . olite parallel to the base. Also yellow color is common in epidote but rare in pyroxene. Remarks : Next to the feldspars pyroxene is the most common constituent of theigneous rocks. Diopside and fassaite (green) are found in contact rocks; also, whatappear to be the same pyroxenes, in many eruptive rocks, as andesites, monzonites, (light green) is found in amphibolites and eclogites (where it may be asso-ciated with a greenish amphibole (smaragdite)). Diallage (bladed and twinned) occursin gabbros and pyroxenites. Common augite (brown) is found in the remaining basiceruptive rocks. In the schists the pyroxene is colorless. Finally augite occurs as a secondary product resulting from the magmatic resorp-tion of hornblende and biotite. Chemical corrosion and mechanical deformation may occur. The green and brownaugites when heated to redness on platinum foil may become red in color. In generalthe pyroxenes are not attacked by acids. H., 5 to 6. Sp. gr., 2,-1 to The Fig. 54. — Diopside, clinopinacoid section. * See p. 85. AMPHIBOLE. gr. of the pyroxenes is considerably higher than that of the amphiboles of similar com-position, hence mechanical separations are possible. Aoiiitf {^-Egirine) (Na pyroxenes).—Occur in green or brown,elongated prismatic crystals, often not very transparent and withmarked pleochroism (like amphibole). Zonal coloring is zonally intergrown with pyroxene the outer zone is elongation is || a (distinction from amphibole whose elonga-tion is II c). The index of refraction is higher than in the otherpyroxenes (;/ = 1-792) and the double refraction stronger {j — a= ). The cxti)iction angle lies in the acute angle and issmall (5°) and the optical character ( — ). The term ^girine-atigitc may be used to describe
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