. A treatise on rocks, rock-weathering and soils;. Petrology; Soils. THE PYROXENITE-AUGITITE GROUP 95 lack of olivine. Following Dr. William's nomenclature, we have the varieties diallagite^ hronzitite, and hyperstlienite, according as the mineral diallage, bronzite, or hypersthene forms the essen- tial constituent. Wehsterite is the name given to the bronzite- diopside variety, occurring near Webster, North Carolina, and hornhlendite to the hornblende-augite variety. The pyroxenites rank, in geological importance, next to the peridotites. Through processes of hydration and other chemical chan
. A treatise on rocks, rock-weathering and soils;. Petrology; Soils. THE PYROXENITE-AUGITITE GROUP 95 lack of olivine. Following Dr. William's nomenclature, we have the varieties diallagite^ hronzitite, and hyperstlienite, according as the mineral diallage, bronzite, or hypersthene forms the essen- tial constituent. Wehsterite is the name given to the bronzite- diopside variety, occurring near Webster, North Carolina, and hornhlendite to the hornblende-augite variety. The pyroxenites rank, in geological importance, next to the peridotites. Through processes of hydration and other chemical changes, they pass into amphibolic and steatitic masses to which the name soapstone or potstone is applied. These last are dark gray or greenish rocks, soft enough to be readily cut with a knife and with a pronounced soapy or greasy feeling; hence the name soapstone. The name potstone was given on account of their having been utilized for making rude pots, for which their softness and fireproof proper- ties render them well qualified. Although it is commonly stated in the text-books that soapstone is a compact form of steatite or talc, few are even approximately pure forms of this mineral, but all contain varying proportions of chlorite, mica, and tremolite, together with perhaps unaltered residuals of pyroxene, granules of iron ore, iron pyrites, quartz, and, in seams and veins, calcite and magnesian carbonates. The variation in chemical composi- tion is shown in the following analyses, I being that of a com- pact, homogeneous-appearing, quite massive variety from Al- berene, in Albemarle County, Virginia, and II one from Frances- town, New Hampshire. Chemical Composition of the Soapstones Constituents Silica (Si02) Alumina (AlgOa) Ferric and ferrous iron (FegOs) and (FeO) Lime (CaO) Magnesia (MgO) Potash (K2O) SodaCNajO) Ignition. (2) AUGITITE The effusive form, augitite, differs from the pyroxenite proper mainly on structural grounds. In common with many lavas it. Please note th
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectpetrolo, bookyear1913
