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Updated: July 6, 2025
These dikes are composed of green, white, and blackish rocks, all porphyritic with feldspar, and often with large crystals of hornblende. The white varieties approach closely in character to andesite, which composes as we have seen, the injected axes of so many of the lines of elevation. Some of the green varieties are finely laminated, parallel to the walls of the dikes.
These veins, two or three inches thick, are distinguished by a fine-grained quartz-granite crossing a coarse-grained granite almost porphyritic, and abounding in fine crystals of red feldspar. I sought in vain, in the Cordillera of Baraguan, for hornblende, and those steatitic masses that characterise several granites of the Higher Alps in Switzerland.
The Rowley Hills in Staffordshire, commonly known as Rowley Ragstone, are melaphyre. This name has usually been extended to all granular mixtures, whether of hornblende and feldspar, or of augite and feldspar. The term DIORITE has been applied exclusively to compounds of hornblende and triclinic feldspar.
I heard one fellow say once that they thought they'd never find gold in hornblende. But they did." California John stumped home in indignant disgust. "Damn little ijits!" he exploded. "Pigheaded! Stubborn as a pair of mules!" The recollection of the scrubbed red cheeks, the clear, puppy-dog, frank brown eyes, the close-curling brown hair, forced his lips to a wry grin.
In an hour after our departure we reached the little island of Majava, which consists of perpendicular strata of a hard, fine-grained, volcanic tufa, with small, bright crystals of hornblende. In three hours we reached Umauas, a dependency of Calbigan.
Lead was procurable from Bactria, Armenia, Korman, and many parts of Affghanistan; orpiment from Bactria, Kerman, and the Hazareh country; antimony from Armenia, Affghanistan, and Media; hornblende, quartz, talc, and asbestos, from various places in the Taurus. Of all necessary minerals probably none was so plentiful and so widely diffused as salt.
If, from these data, it is inferred that the same substance may assume the crystalline forms of hornblende or augite indifferently, according to the more or less rapid cooling of the melted mass, it is nevertheless certain that the variety commonly called augite, and recognised by a peculiar crystalline form, has usually more lime in it, and less alumina, than that called hornblende, although the quantities of these elements do not seem to be always the same.
The strike is generally to the northeast, the direction we are going. About Losito we found the trap had given place to hornblende schist, mica schist, and various schorly rocks. We had now come into the region in which the appearance of the rocks conveys the impression of a great force having acted along the bed of the Zambesi.
In common sand, the quartz grains are the most numerous; but this is not a proof that the rocks from which these particles were derived were wholly, or even chiefly, quartzose in character; for, in many composite rocks, as, for example, in the granitic group, the mica, feldspar, and hornblende are more easily decomposed by chemical action, or disintegrated, comminuted, and reduced to an impalpable state by mechanical force, than the quartz.
The gneiss close to the fragments generally contained many large crystals of hornblende, which are entirely absent or rare in other parts: its folia or laminae were gently bent round the fragments, in the same manner as they sometimes are round concretions.
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