Pectolite is a sodium-calcium chain silicate that occurs worldwide as white to gray fibrous radiating sprays in basalt vesicles and serpentinite. Its rare blue copper-substituted variety from the Dominican Republic is sold as the gem larimar.
Properties
- Formula: NaCa2Si3O8(OH)
- Crystal system: Triclinic
- Hardness: 4.5 – 5
- Color: White, gray, occasionally pink (manganoan), blue (cuprian = larimar)
- Streak: White
- Luster: Vitreous to silky
- Cleavage: Perfect on {100} and {001}
- Density: 2.7 – 2.9 g/cm³
Occurrence
Worldwide in basalt vesicles and serpentinite. Notable localities: Paterson and Prospect Park (New Jersey), Mont Saint-Hilaire (Quebec), Bombay quarries (India), and as the cuprian variety larimar at Barahona (Dominican Rep.). China hosts pectolite in Hebei traprocks but not in collector grade.
Identification
White radiating fibrous sprays + association with prehnite/zeolites in basalt + sharp prismatic cleavage. Distinguish from natrolite (also fibrous but harder, more glassy) by density and chemistry.
Collector Notes
Excellent radiating “porcupine” balls of pectolite from New Jersey traprocks have been classics of American collecting since the 19th century. The cuprian variety (larimar) is the famous gem-trade form.
Found at these Localities
- Filipinas Mine (Los Chupaderos) (菲利皮纳斯矿(拉利玛产地))
- Mont Saint-Hilaire (圣希莱尔山(魁北克))
- Maharashtra Deccan Traprock Zeolites (马哈拉施特拉德干玄武岩沸石产地)
