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ACHITE, or AEGIRITE

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Originally appearing in Volume V01, Page 149 of the 1911 Encyclopedia Britannica.

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ACHITE, or AEGIRITE

ACHITE, or AEGIRITE , a See also:

MINERAL

mineral of the See also:

PYROXENE

pyroxene (q.v.) See also:

GROUP

group, Which may be described as a soda-pyroxene, being essentially asodium and ferric metasilicate, NaFe(SiOs)2. In its crystallographic characters it is See also:

close to See also:

ORDINARY (med. Lat. ordinarius, Fr. ordinaire)

ordinary pyroxene (See also:

AUGITE

augite and See also:

DIOPSIDE

diopside), being See also:

MONOCLINIC

monoclinic and having nearly the same See also:

ANGLE (from the Lat. angulus, a corner, a diminutive, of which the primitive form, angus, does not occur in Latin; cognate are the Lat. angere, to compress into a bend or to strangle, and the Gr. ayKOS, a bend; both connected with the Aryan root ank-, to

angle between the prismatic cleavages. There are, however, important See also:

DIFFERENCES, CALCULUS OF (Theory of Finite Differences)

differences in the See also:

OPTICAL

optical characters: the birefringence of acmite is negative, the pleochroism is strong and the extinction angle on the See also:

PLANE

plane of symmetry measured to the See also:

VERTICAL (from Lat. vertex, highest point)

vertical See also:

AXIS (Lat. for " axle ")

axis is small (3°-5°). The hardness is 6-0, and the specific gravity 3'55. Crystals are elongated in the direction of the vertical axis, and are blackish See also:

green (aegirite) or dark See also:

brown (acmite) in See also:

COLOUR (Lat. color, connected with celare, to hide, the root meaning, therefore, being that of a covering)

colour. Being isomorphous with augite, crystals intermediate in See also:

composition between augite or diopside and aegirite are not uncommon, and these are known as aegirine-augite or aegirinediopside. Acmite is a characteristic constituent of igneous rocks See also:

rich in soda, such as See also:

NEPHELINE

nepheline-syenites, phonolites, &c. It was first discovered as slender crystals, sometimes a See also:

FOOT

foot in length, in the See also:

PEGMATITE (from Gr. 1r3 y ea, a bond)

pegmatite See also:

VEINS

veins of the See also:

GRANITE (adapted from the Ital. granite, grained; Lat. granum, grain)

granite of Rundemyr, near See also:

KONGSBERG

Kongsberg in See also:

Norway, and was named by F. Stromeyer in 1821 from the Gr. aKo, a point, in allusion to the pointed terminations of the crystals. Aegirite (named from Aegir, the Scandinavian See also:

sea-See also:

god) was described in 1835 from the elaeolite-See also:

SYENITE

syenite of See also:

SOUTHERN

southern Norway. Although exhibiting certain varietal differences, the essential-identity of acmite and aegirite has See also:

long been established, but the latter and more See also:

RECENT

recent name is perhaps in more See also:

general use, especially among petrologists.

End of Article: ACHITE, or AEGIRITE

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