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Formula: NaCa2Si3O8(OH)
Inosilicate (chain silicate), single width,
wollastonite group, forms a series with
serandite
Crystal System: Triclinic
Specific gravity: 2.84 to 2.9 meaasured, 2.87 calculated
Hardness: 4½ to 5
Streak: White
Colour: White, grey, sometimes greenish, yellowish, colourless
Solubility: Slightly soluble in hydrochloric acid
Environments:
Plutonic igneous environments
Basaltic cavities
Pectolite is a secondary mineral similar in occurrence to
zeolites. It is found lining cavities in
basalt, associated
with zeolites,
prehnite and
calcite.
Localities
At the Cowgreen Dam quarry, Forest and Frith, County Durham, England, UK, veins were exposed composed of pectolite, with lenses of
calcite, forming radiating crystalline bands parallel to the vein walls, and clusters of radiating
crystals up to 10 mm across were found coating joints in dolerite
(JRS 21.9-11).
At Force Garth Quarry, Forest and Frith, County Durham, England, UK, stevensite
pseudomorphs after pectolite have been found
(JRS 21.9-11).
At High Force Quarry, Forest and Frith, County Durham, England, UK, pectolite typically occurs as thin coatings of aggregates of
radiating crystals, up to 100 mm across, coating joint surfaces. Stevensite
pseudomorphs after pectolite have also been found here
(JRS 21.9-11).
At Middleton-in-Teesdale, County Durham, England, UK, discontinuous veins of pectolite are comparatively common in the abandoned
quarries, and stevensite pseudomorphs after
pectolite have also been found here
(JRS 21.9-11).
At Copthill Quarry, Stanhope, County Durham, England, UK, pectolite occurs as fine specimens of radiating joint coatings.
Pseudomorphs of both calcite and
quartz after pectolite have been found here
(JRS 21.9-11, SY p164).
At Cambokeels Mine, Westgate, Stanhope, County Durham, England, UK, pectolite has been found as radiating coatings on
dolerite from the same part of the workings that yielded
analcime and apophyllite
(JRS 21.9-11).
At Barrasford Quarry, Chollerton, Northumberland, England, UK, stevensite
pseudomorphs after pectolite have been found
(JRS 21.9-11).
At the Clee Hill quarry, Titterstone Clee Hill, Shropshire, England, UK, pectolite has been found on
dolerite
(RES p296).
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