Scolecite is a
tectosilicate mineral belonging to the
zeolite group; a hydrated
calcium silicate, CaAl2Si3O10·3H2O. Its name came from the Greek word, skolec = 'worm' because of its reaction to the blowpipe flame. It is a calcium zeolite, and like the sodium-zeolite
natrolite and the sodium-calcium zeolite
mesolite, usually occurs as acicular and fibrous aggregations. Although having nearly the same interfacial angles as the orthorhombic natrolite, it
crystallizes in the
monoclinic system, and, as shown by the etched figures and the pyroelectric character, in the hemibedral class of this system, there being a plane, but no axis, of symmetry. Scolecite can therefore be distinguished from natrolite by an 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 colorless or white, transparent, and vitreous in luster. It has a
Mohs hardness is 5 and a
specific gravity 2.2. It is a mineral of secondary origin, and occurs with other zeolites in the amygdaloidal cavities of weathered
volcanic rocks of basic composition. Associated minerals are
quartz,
apophyllite,
babingtonite,
heulandite,
stilbite and other zeolites. It was first described from Kaiserstuhl in
Baden in 1813. Fine divergent groups of prismatic crystals are found in the
basalt of Berufjord near Djupivogr in
Iceland and in the
Deccan Traps near
Pune in
India; hence the synonym poonahlite for this species. Other occurrences include
Riverside County, California;
Skye,
Scotland and
Santa Catarina, Brazil. The name is from the
Greek, skolec for worm in reference to the mineral's reaction to the blowpipe flame.
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General Information:
Chemical Formula:
CaAl2Si3O10·3(H2O)
Composition:
(Molecular Weight = 392.34 gm)
Calcium 10.22 %
CaAluminum 13.75 %
AlSilicon 21.48 %
SiHydrogen 1.54 %
H Oxygen 53.01 %
O Empirical Formula:
CaAl2Si3O10·3(H2O)
Environment:
Low tempurature alteration of basalts and related rocks.
IMA Status:
Approved IMA
Locality:
Kaiserstuhl in Baden.
Name Origin:
From the Greek, skolec = 'worm' in reference to the mineral's reaction to the blowpipe flame.
Physical Properties:
Cleavage:
[110] Perfect
Color:
brownish, colorless, or white.
Density:
2.16 - 2.4, Average = 2.28
Diaphaniety:
Transparent to subtranslucent
Habits:
Massive - Fibrous - Distinctly fibrous fine-grained forms., Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite),
Hardness:
5-5.5 - Apatite-Knife Blade
Luminescence:
Non-fluorescent.
Luster:
Vitreous - Silky
Streak:
white
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