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BRUCITE

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Originally appearing in Volume V04, Page 677 of the 1911 Encyclopedia Britannica.
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BRUCITE , a See also:

mineral consisting of See also:magnesium hydroxide, Mg(OH)2, and crystallizing in the See also:rhombohedral See also:system. It was first described in 1814 as " native See also:magnesia from New See also:Jersey by A. See also:Bruce, an See also:American mineralogist, after whom the See also:species was named by F. S. See also:Beudant in 1824; the same name had, however, been earlier applied to the mineral now known as chondrodite. Brucite is usually found as platy masses, some-times of considerable See also:size, which have a perfect cleavage parallel to the See also:surface of the plates. It is See also:white, sometimes with a tinge of See also:grey, See also:blue or See also:green, varies from transparent to translucent, and on the cleavage surfaces has a pronounced pearly lustre. In See also:general See also:appearance and softness (H= 2Z) it is thus not unlike See also:gypsum or See also:talc, but it may be readily distinguished from these by its See also:optical See also:character, being uniaxial with See also:positive birefringence, whilst gypsum is biaxial and talc has negative birefringence. The specific gravity is 2.38–2.40. In the variety known as nemalite the structure is finely fibrous and the lustre silky: this variety contains 5 to 8 % of ferrous See also:oxide replacing magnesia, and has consequently a rather higher specific gravity, viz. 2.45. Another variety, manganbrucite, has the magnesia partly replaced by manganous oxide (14 %), and thus forms a passage to the isomorphous mineral pyrochroite, Mn(OH)2.

Brucite is generally associated with other magnesian minerals, such as See also:

magnesite and See also:dolomite, and is commonly found in See also:serpentine, or sometimes as small scales in phyllites and crystal-See also:line See also:schists; it has also been observed in metamorphosed magnesian See also:limestone, such as the See also:rock known as predazzite from Predazzo in See also:Tirol. The best crystals and foliated masses are from See also:Texas in See also:Pennsylvania, U.S.A., and from Swinaness in Unst, one of the See also:Shetland Isles, Nemalite is from See also:Hoboken, New Jersey, and from See also:Afghanistan. At all these localities the mineral forms See also:veins in serpentine. (L. J.

End of Article: BRUCITE

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