"Porphyritic" Quotes from Famous Books
 ... 10. Dyke, porphyritic granite, composed of white quartz, white feldspar, and bronze-coloured mica. This dyke cuts across the schistus last mentioned, in a direction north-east and south-west. It is nearly vertical, and varies in breadth from nine to ...
— Account of a Voyage of Discovery - to the West Coast of Corea, and the Great Loo-Choo Island • Captain Basil Hall
... the British general determined to seize that point. Majuba is composed of alternate strata of sandstone and shale lying nearly horizontal and capped—as is often the case in these mountains—by a bed of hard igneous rock (a porphyritic greenstone). The top is less than a mile in circumference, depressed some sixty or seventy feet in the centre, so as to form a sort of saucer-like basin. Here has been built a tiny cemetery, in which some of the British soldiers ...
— Impressions of South Africa • James Bryce
... probable existence of coal in the vicinity; following the series appears a compact, fine-grained amorphous sandstone, having an almost flinty fracture; this rock, in a few miles, gives place to granite and gneiss, frequently broken up by the upheaval of whinstone and porphyritic trap hills, having an elevation of from 100 to 500 ...
— Journals of Australian Explorations • A C and F T Gregory
... horseshoe and close up to it stand the famous blue-stones, now twelve in number, but originally perhaps more. These stones are not so high as the trilithons, the tallest reaching only 7-1/2 feet. They are nearly all of porphyritic diabase. It has often been asserted that these blue-stones must have been brought to Stonehenge from a distance, as they do not occur anywhere in the district. Some have suggested that they came from Wales or Cornwall, or even by sea from Ireland. Now, the recent excavations ...
— Rough Stone Monuments and Their Builders • T. Eric Peet
... present shells of Patagonia. This bed contains an ENORMOUS field of lava. This is of some interest, as being a rude approximation to the age of the volcanic part of the great range of the Andes. Long before this it existed as a slate and porphyritic line of hills. I have collected a tolerable quantity of information respecting the period and forms of elevations of these plains. I think these will be interesting to Mr. Lyell; I had deferred reading his third volume till my return: you may guess ...
— More Letters of Charles Darwin - Volume I (of II) • Charles Darwin
... tell you it is all the same, only less easily understood; and therefore more scientific). Then the Leaf- crystals, as I said, form an immense mass of foliated rocks; and the Granular crystals, which are of many kinds, form essentially granular, or granitic and porphyritic rocks; and it is always a point of more interest to me (and I think will ultimately be to you), to consider the causes which force a given mineral to take any one of these three general forms, than what the peculiar geometrical limitations are, belonging to its own crystals. [Footnote: ...
— The Ethics of the Dust • John Ruskin |
