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Bible Encyclopedias
Hornblende
1911 Encyclopedia Britannica
or an important member of the amphibole group of rock-forming minerals. The name is an old one of German origin, and was used for any dark-coloured prismatic cr y stals from which metals could not be extracted. It is now applied to the dark-coloured aluminous members of the monoclinic amphiboles, occupying in this group the same position that augite occupies in the pyroxene group. The monoclinic crystals are prismatic in habit with a six-sided cross-section; the angle between the prismfaces (M), parallel to which there are perfect cleavages, is 55° 49'The colour (green, brown or black) and the specific gravity (3.0-3.3) vary with the amount of iron present. The pleochroism is always strong, and the angle of optical extinction on the plane of symmetry (x in the figure) varies from o° to 37°. The chemical composition is expressed by mixtures in varying proportions of the molecules Ca(Mg,Fe)3(S103)4, (Mg,Fe) (AI,Fe) 2 SiO 6 and NaAI(S103)2Numerous varieties have been distinguished by special names: edenite, from Edenville in New York, is a pale-coloured aluminous amphibole containing little iron; pargasite, from Pargas near Abo in Finland, a green or bluish-green variety; common hornblende includes the greenish-black and black kinds containing more iron. The dark.-coloured porphyritic crystals of basalts are known as basaltic hornblende.
Hornblende occurs as an essential constituent of many kinds 1 Buffon, as was his manner, enlarges on the cruel injustice done to these birds by Nature in encumbering them with this deformity, which he declares must hinder .them from getting their food with ease. The only corroboration his perverted view receives is afforded by the observed fact that hornbills, in captivity at any rate, never have any fat about them.
2 In The Malay Archipelago (i. 213), Wallace describes a nestling hornbill (B. bicornis) which he obtained as "a most curious object, as large as a pigeon, but without a particle of plumage on any part of it. It was exceedingly plump and soft, and with a semi-transparent skin, so that it looked more like a bag of jelly, with head and feet stuck on, than like a real bird." of igneous rocks, such as hornblende-granite, syenite, diorite, hornblende-andesite, basalt, &c.; and in many crystalline schists, for example, amphibolite and hornblende-schist which are composed almost entirely of this mineral. Well-crystallized specimens are met with at many localities, for example: brilliant black crystals (syntagmatite) with augite and mica in the sanidine bombs of Monte Somma, Vesuvius; large crystals at Arendal in Norway, and at several places in the state of New York; isolated crystals from the basalts of Bohemia. (L. J. S.)
These files are public domain.
Chisholm, Hugh, General Editor. Entry for 'Hornblende'. 1911 Encyclopedia Britanica. https://www.studylight.org/encyclopedias/eng/bri/h/hornblende.html. 1910.
