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abundant acid aggregates alkalies alteration alumina Amer analyses andesites applied augite basaltic basaltic rocks basic biotite breccias Bull calcareous calcite called carbonate chemical cherts chiefly chlorite clay cleavage coarse Compare conglomerates crystals dacites dark silicates deposits developed diabase diorites dolomite especially feldspar felsitic FeO CaO MgO finely crystalline fragments gabbro garnet geological glass gneisses granite granitoid rocks groundmass hornblende Idem igneous rocks intrusion iron Jahrb Jour kaolin lavas less leucite lime limestones magma magnesia magnetite masses metamorphic rocks mica mica-schists microscopic Mineralogical Composition minerals muscovite name for rocks name given name is derived name proposed nepheline nepheline-syenites Obsidian olivine original orthoclase oxides peridotite phenocrysts phonolites plagioclase plutonic porphyritic porphyritic rocks prefixed pyroxene pyroxenites quartz quartz-porphyries quartzites rhyolites rocks consisting Rosenbusch sandstones schists sedimentary sediments serpentine shales silicates SiO2 slates soda suggested Surv syenites synonym term texture tourmaline trachytes tuffs U. S. Geol variety volcanic yield
Page 123 - Its restricted sense for porphyritlc and felsitic rocks consisting of augite, olivine and plagioclase with varying amounts of a glassy base which may entirely disappear. In a broader sense the basalt or basaltic group is used to include all the dark, basic, volcanic rocks, such as the true basalts; the uepheline-, leucite-, and melillte-basalts; the augitltes and llmburgites; the diabases, and melaphyres.
Page 128 - Intrusions and their walls. The word Is of wide use In western mining regions on account of the frequent occurrence of ore bodies along contacts. (Kemp) 2. (So. Afr.) A lode of great length and between two kinds of rocks, ope of which Is generally an igneous intrusive.
Page 138 - Granite. — A granitoid igneous rock consisting of quartz, orthoclase, more or less oligoclase, biotite, and muscovite. Granitoid. — A textural term to describe those igneous rocks which are entirely composed of recognizable minerals.
Page 65 - ... is little else than these two. No. 19 is practically pure kaolin. Mineralogical Composition. Varieties. The argillaceous sandstones have a finer grain than the sandstones proper, and tend to form thin but tough beds. They find their best examples in the flagstones of our eastern cities. Shales lack this coherence and break readily into irregular slabs and wedge-shaped fragments of no notable size. As sands give rise to sandstones, so on hardening and drying, muds and silt yield shales. Shales...
Page 149 - Marl. A calcareous clay, or intimate mixture of clay and particles of calcite or dolomite, usually fragments of shells. Marl in America is chiefly applied to incoherent sands, but abroad compact, impure limestones are also called marls.
Page 124 - Having the odor of bitumen. Often applied to minerals (Dana). Bituminous cement. — A bituminous material suitable for use as a binder, having cementing qualities which are dependent mainly on its bituminous character (Bacon). Bituminous concrete pavement.
Page 148 - as consisting essentially of diopside and a magnesia-potash mica with leucite in decidedly subordinate amount. Its magma is low in silica, alumina and iron, rich in potash, and contains so much lime and magnesia that silicates of these bases are the principal constituents, yet controlled in their development by the strong potash element.
Page 74 - When plant tissue accumulates in damp places and under a protecting layer of water that prevents too rapid oxidation, new accessions may more than compensate for loss by decay so that extensive deposits may result. These become progressively rich in carbon by the loss of their other elements and yield beds of considerable geological, but much greater practical importance. The course of the changes and the several stages are indicated in the following table. CHON Total. Woody Tissue 50 6. 43 I.
Page 162 - The name of the mineral is often prefixed to the name of the rock containing it, as, mtca-basult, mica-tinguaite, mica-trachyte, etc.
Page 1 - Rock-salt, ice, calcite, serpentine, cemented fragments of quartz, kaolin and a few others are in sufficient quantity, but the vast majority of rocks consist of two or more. The condition that a rock should form an essential part of the earth is introduced to bar out those minerals or aggregates which, though important in themselves, are none the less insignificant as entering into the mass of the globe. Thus the sulphide ores, while locally often in considerable quantity, when broadly viewed are...