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Pectolite  (Larimar)
Current inventory:  1 gem
 

Chemistry:  NaCa₂(Si₃O₈)(OH)

Discovered in 1828;   IMA status: Valid (pre-IMA; Grandfathered).
Pectolite gets its name from the Greek pektos, meaning congealed because of the translucent appearance the mineral sometimes has.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/F.18-60

8 : Silicates
F : Inosilicates (chain and band) double chains [Si2O6]4-
18 : Wollastonite-2M - Foshagite series

Crystal Data

Crystallography:

Triclinic - Pinacoidal

Crystal Habit:

Crystals may be tabular, but also commonly acicular, to 15 cm; radiating fibrous, spheroidal, or columnar; fine-grained, massive. Twinning: Twin axis [010] with composition plane [100], common.

Physical Properties

Cleavage:

[100] Perfect; [001] Perfect

Fracture:

Splintery

Tenacity:

Brittle

Moh's Hardness:

4.5 - 5.0

Density:

2.74 - 2.88 (g/cm³)

Luminescence:

Fluorescent, pink under SW UV, orange-pink under LW UV; may be Triboluminescent 

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colourless, white, pale pink, greenish, pale to dark blue

Transparency:

Transparent to Translucent, Subtranslucent, Opaque

Luster:

Vitreous to Silky

Refractive Index:

1.594 - 1.642  Biaxial ( + )

Birefringence:

0.037

Dispersion:

Very Weak

Pleochroism:

n/a

Occurances

Geological Setting:

A primary mineral in nepheline syenites. A hydrothermal mineral in cavities in basalts and diabases; in serpentinites and peridotites; from metamorphosed high-calcium rocks.

Type Locality:

Sano, Mori, Mt. Baldo, Trento Province, Trentino-Alto Adige, Italy

Year Discovered:

1828

View mineral photos:

Pectolite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Most Pectolite is found as opaque massive material that takes a good shine and is suitable for cabochons. Larimar is a beautiful pale to dark blue type of Pectolite from the Dominican Republic. The blue color is due to copper. Larimar is the trade name for Pectolite only from this location and is considered the best and most beautiful Pectolite cabochon material in the world. Several other locations worldwide also produce opaque material suitable for cabochons but these are usually white to gray. Material from Magnet Cove, Arkansas, USA and Greenland is a pale pink due to manganese. The only source of transparent Pectolite crystals that could be faceted is the Thetford Mines, Quebec, Canada. A very small find there in 1973 produced pale blue-green and colorless crystals up to 5 inches long. Only a few faceted gems have been cut from this find and are the only known faceted Pectolite gems known to exist.
 

  
Pectolite (Larimar) gems for sale: