 |
Chemical Formula | NaCa2Si3O8(OH) | ||||||||
|
Composition | Hydrous sodium calcium silicate, sometimes with some manganese | ||||||||
|
Variable Formula | Na(Ca,Mn)2Si3O8(OH) | ||||||||
|
Color | White, colorless, gray, light yellow, light brown, light blue, light pink. Some specimens tarnish black or brown upon exposure to air. | ||||||||
|
Streak | White | ||||||||
|
Hardness | 4½ - 5 (Usually difficult to determine because of the splintery crystals) | ||||||||
|
Crystal Forms and Aggregates |
(Triclinic) Single crystals are extremely rare. When they do occur, they are elongated prismatic splinters, and are usually protrusions from dense radiating aggregates. However, small, flat, single blades have recently been found. Pectolite occurs fibrous, mammilary, radiating, in fibrous and globular masses, and in radiating veins. | ||||||||
|
Transparency | Transparent to translucent | ||||||||
|
Specific Gravity | 2.7 - 2.9 | ||||||||
|
Luster | Vitreous | ||||||||
|
Cleavage | 2,2 - forming at an angle near 90º | ||||||||
|
Fracture | Splintery, uneven | ||||||||
|
Tenacity | Brittle | ||||||||
|
Other ID Marks | Usually fluoresces yellow or orange in longwave ultraviolet light | ||||||||
|
Varieties |  Larimar - Light blue
variety from the Dominican Republic |
||||||||
|
In Group | Silicates ; Inosilicates | ||||||||
|
All About | Pectolite occurs in cavities of basalt in igneous environments, and is almost always associated
with zeolites. Pectolite crystals are usually tiny, slender, elongated fibers radiating from a central point outwards. When the fibers are densely aggregated, they from a globular mass. These specimens should not be handled, as they give off splinters which are very hard to remove from the hand. |
||||||||
|
Uses | Pectolite is popular among mineral collectors for its interesting radiating "blobs". The light blue variety Larimar is used as a gem. | ||||||||
|
Striking Features | Crystal habits and mineral associations | ||||||||
|
Complex Tests | Soluble in hydrochloric acid | ||||||||
|
Popularity (1-4) | 2 | ||||||||
|
Prevalence (1-3) | 2 | ||||||||
|
Demand (1-3) | 2 | ||||||||
|
Distinguishing Similar Minerals |
Wollastonite - occurs in different environments Tremolite - slightly harder (5 - 6), usually flexible, occurs in different environments Natrolite - individual crystals are usually larger and aggregated less densely; otherwise difficult to distinguish Mesolite - individual crystals are usually aggregated less densely; otherwise difficult to distinguish |
||||||||
|
Commonly Occurs With |
Prehnite, Datolite, Apophyllite, Stilbite, Heulandite, Chabazite, Natrolite, Serpentine, Calcite | ||||||||
|
Noteworthy Localities |
Worldwide localities include the Kola
Peninsula, Russia; Bohemia, Czech Republic; Disco Island,
Greenland; and Trento, Italy. The unique, light blue gem variety "Larimar" is found only in the Dominican Republic. The finest specimens for this mineral occur in the trap rock basalts of northern New Jersey, in the following locations: Paterson, Passaic Co. Prospect Park, Passaic Co. Millington, Morris Co. Bergen Hill, Hudson Co. Other U.S. occurrences of this mineral are Magnet Cove, Garland Co., Arkansas, and Middletown, Lake Co., California. Pink, waterworn pebbles are found on the beach of Island Royale in Lake Superior. Small amounts have also been found in the Golden Gate area of California. In Canada, two localities have produced small, individual crystal blades, and they are the Jeffery Quarry, Asbestos, Quebec, and Mont Saint Hilaire, Quebec. |
||||||||
|
Picture Icon Links |
|
||||||||
|
Picture Links | 1. Radiating
needles 2. Fibrous needles 3. Pectolite variety Larimar |
