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SCOLECITE

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Originally appearing in Volume V24, Page 407 of the 1911 Encyclopedia Britannica.
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SCOLECITE , a See also:

mineral belonging to the zeolite See also:group; a hydrated See also:calcium silicate, CaAl2Si3Oio+3H20. It is a See also:lime-zeolite, and like the soda-zeolite See also:natrolite and the soda-limezeolite mesolite, usually occurs as acicular and fibrous aggregations. Although having nearly the same interfacial angles as the orthorhombic natrolite, it crystallizes in the See also:monoclinic See also:system, and, as shown by the etched figures and the pyroelectric See also:character, in the hemihedral class of this system, there being a See also:plane, but no See also:axis, of symmetry. Scolecite can therefore be distinguished from natrolite by an See also:optical examination, since the acicular crystals do not extinguish parallel to their length between crossed nicols. Twinning on the ortho-pinacoid is usually evident. The mineral is colourless or See also:white, transparent, and vitreous in lustre: the hardness is 52, and the specific gravity 2.2. It is a mineral of secondary origin, and occurs with other See also:zeolites in the amygdaloidal cavities of weathered volcanic rocks of basic See also:composition. See also:Fine divergent See also:groups of prismatic crystals are found in the See also:basalt of Berufjord near Djupivogr in See also:Iceland and in the See also:Deccan traps near See also:Poona in See also:India; hence the synonym poonahlite for this See also:species. The name scolecite is derived from Gr. arcwAnE, a See also:worm, because the crystals sometimes curl up like See also:worms when heated before the See also:blowpipe. (L. J.

End of Article: SCOLECITE

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