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Formula: Ca(Si3Al2)O10.3H2O
Tectosilicate (framework silicate),
zeolite group
Crystal System: Monoclinic
Specific gravity: 2.25 to 2.29 measured, 2.275 calculated
Hardness: 5 to 5½
Streak: White
Colour: Colourless, white, pink, salmon, red, green
Solubility: Soluble in common acids
Common impurities: Na,K
Environments:
Metamorphic environments
Hydrothermal environments
Basaltic cavities
Scolecite occurs in basalt,
andesite, gneiss, and
amphibolite, in
contact metamorphic and in
hydrothermal environments. It is associated with other
zeolites, calcite,
quartz and prehnite
(Dana).
Localities
At the Marron Volcanics of the Olalla Area South-Central British Columbia, Canada, Compact masses of colour-zoned
(salmon-pink-white) acicular scolecite completely fill vesicles to 10 cm long in the road cuts and the upper areas
at Yellow Lake. Some terminations are mesolite, but the bulk of this type of
occurrence consists of scolecite
(R&M 96.6.524).
At Charcas, Charcas Municipality, San Luis Potosí, Mexico,
the primary minerals are
sphalerite, galena,
chalcopyrite, bornite,
tetrahedrite,
arsenopyrite, pyrite and
silver minerals such as jalpaite,
diaphorite and acanthite. In
the host rock, as metamorphic or alteration minerals, danburite,
datolite, hedenbergite,
epidote, chlorite,
andradite, actinolite
and wollastonite have been reported.
Quartz, calcite and
danburite crystallised during the entire life of the systems, throughout
the intrusive emplacement, metamorphism, and mineralising events. With depth, both
sphalerite and galena decrease
while chalcopyrite increases.
Secondary sulphides formed include
bornite, covellite,
digenite and chalcocite.
Native silver, native gold,
hematite and goethite were
deposited after the sulphides
(Minrec 55.6.727-728).
Scolecite occurs as white, glassy, acicular, well terminated crystals up to 4 cm long, forming sprays and
hemispherical aggregates. It can cover white botryoidal datolite, white
danburite crystals or blocky rhombohedral
calcite crystals on matrix of sedimentary rock
(Minrec 55.6.769-770).
In Eritrea scolecite has been reported in weathered basalt, associated with
stilbite and calcite
(DHZ 4 p375).
Near a pegmatite at Valle Maggia, Switzerland, scolecite occurs in crevices in biotite
gneiss associated with K-feldspar variety
adularia,
epidote and chlorite
(DHZ 4 p375).
On the Isle of Mull, Scotland, UK, scolecite occurs in profusion in basaltic cavities, and is often the final product of
the sequence
albite → chlorite →
epidote → prehnite →
scolecite
though in some cavities heulandite succeeds
scolecite
(DHZ 4 p375).
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