A radiating fibrous mass of Pectolite
A close-up view.
CHEMISTRY NaCa2Si3O8(OH) Sodium calcium silicate
CRYSTALLOGRAPHY Triclinic
CRYSTAL GROWTH AND HABITS Pectolite commonly forms acicular crystals that form radiating masses. Crystals may also be tabular. Pectolite may also be fine grained to massive.
COLOR AND OTHER OPTICAL PROPERTIES Colorless to white, gray to yellowish, translucent to opaque, may be triboluminescent
HARDNESS 4.5 -5 SPECIFIC GRAVITY 2.7 - 2.9
LUSTER Silky to sub vitreous STREAK White
BREAKABILITY Pectolite has 2 very good cleavage directions that allow the material to break very easily - making it difficult to determine hardness. It is tough when in compact masses and has an uneven fracture. It is also brittle.
OCCURRENCE Pectolite is often found is association with zeolites in basalt but it can also form as a secondary mineral derived from metamorphosed calcium rich rocks.
ASSOCIATED MINERALS Zeolites, Datolite, Prehnite