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HUMITE , a See also:group of minerals consisting of basic See also:magnesium fluo-silicates, with the following formulae: Chondrodite, Mg3[Mg(F,OH)]2[SiO4]2; Humite, Mg5[Mg(F,OH)]2[SiO4]3; Clinohumite, Mg7[Mg(F,OH)]2[SiO4]4. Humite crystallizes in the orthorhombic and the two others in the See also:monoclinic See also:system, but between them there is a See also:close crystallographic relation: the
lengths of the See also:vertical axes are in the ratio 51:9, and this is also the ratio of the number of magnesium atoms See also:present in each of the three minerals. These minerals are strikingly similar in See also:appearance, and can only be distinguished by the goniometric measurement of the complex crystals. They are See also:honey-yellow to See also:- BROWN
- BROWN, CHARLES BROCKDEN (1771-181o)
- BROWN, FORD MADOX (1821-1893)
- BROWN, FRANCIS (1849- )
- BROWN, GEORGE (1818-188o)
- BROWN, HENRY KIRKE (1814-1886)
- BROWN, JACOB (1775–1828)
- BROWN, JOHN (1715–1766)
- BROWN, JOHN (1722-1787)
- BROWN, JOHN (1735–1788)
- BROWN, JOHN (1784–1858)
- BROWN, JOHN (1800-1859)
- BROWN, JOHN (1810—1882)
- BROWN, JOHN GEORGE (1831— )
- BROWN, ROBERT (1773-1858)
- BROWN, SAMUEL MORISON (1817—1856)
- BROWN, SIR GEORGE (1790-1865)
- BROWN, SIR JOHN (1816-1896)
- BROWN, SIR WILLIAM, BART
- BROWN, THOMAS (1663-1704)
- BROWN, THOMAS (1778-1820)
- BROWN, THOMAS EDWARD (1830-1897)
- BROWN, WILLIAM LAURENCE (1755–1830)
brown or red in See also:colour, and have a vitreous to resinous lustre; the hardness is 6-6zi and the specific gravity 3.1-3.2. Further, they often occur associated together, and it is only comparatively recently that the three See also:species have been properly discriminated. The name humite, after See also:Sir See also:Abraham See also:Hume, See also:Bart. (1749-1839), whose collection of See also:diamond crystals is preserved at See also:Cambridge in the University museum, was given by the See also:comte de Bournon in 1813 to the small and brilliant honey-yellow crystals found in the blocks of crystalline See also:limestone ejected from See also:Monte Somma, See also:Vesuvius; all three species have since been recognized at this locality. Chondrodite (from x6pbpos, " a See also:grain ") was a name See also:early (1817) in use for granular forms of these minerals found embedded in crystalline limestones in See also:Sweden, See also:Finland and at several See also:place in New See also:York and New See also:Jersey. Large See also:hyacinth-red crystals of all three species are associated with See also:magnetite in the See also:Tilly See also:Foster See also:iron-mine at See also:Brewster, New York; and at Kafveltorp in See also:Orebro, Sweden, similar crystals (of chondrodite) occur em-bedded in See also:galena and chalcopyrite.
The relation mentioned above between the crystallographic constants and the chemical See also:composition is unique amongst minerals, and is known as a morphotropic relation. S. L. Penfield and W. T. H. See also:Howe, who in 1894 noticed this relation, predicted the existence of another member of the See also:series, the crystals of which would have a still shorter vertical See also:axis and contain less magnesium, the See also:formula being Mg[Mg(F,OH)]2SiO4; this has since been discovered and named prolectite (from irpoXEyecv, " to foretell "). (L. J.
End of Article: HUMITE
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