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Pectolite
Chemical Formula	NaCa2Si3O8(OH)
Species	Silicates
Crystal System	Triclinic
Mohs Scale	4-5
Specific Gravity	2.84-2.90
Color	Colorless, whitish, grayish, yellowish
Streak	White
Luster	Sub-Vitreous, Silky
Refractive Index	n = 1.594 - 1.610 n = 1.603 - 1.614 n = 1.631 - 1.642
Diaphaneity	Transparent, Translucent
Cleavage	Perfecton and
Fracture	Irregular/Uneven
Crystal Habit：Tabular to acicular, radiating fibrous, spheroidal, or columnar; massive
Geological Setting：Primary mineral in nepheline syenites. Hydrothermal mineral in cavities in basalts and diabases. In serpentinites and peridotites.

Pectolite is a white to gray mineral, NaCa₂Si₃O₈(OH), sodium calcium inosilicate hydroxide. It crystallizes in the triclinic system typically occurring in radiated or fibrous crystalline masses. It has a Mohs hardness of 4.5 to 5 and a specific gravity of 2.7 to 2.9. The gemstone variety, larimar, is a pale to sky blue.

Occurrence

It was first described in 1828 at Mt. Baldo, Trento Province, Italy and named from the Greek pektos – "compacted" and lithos – "stone".

It occurs as a primary mineral in nepheline syenites, within hydrothermal cavities in basalts and diabase and in serpentinites in association with zeolites, datolite, prehnite, calcite and serpentine. It is found in a wide variety of worldwide locations.