PECTOLITE: “Larimar” Dominican Republic (cabochons, ~6 to 30 carat)
Fibrous material has a chatoyancy that gives a catseye effect to cabochons. Pectolite is a curiosity for collectors. The fibrous agregates are seldom cohesive enough to cut, and the material is too soft and fragile for wear, unless the fibers are intergrown. Such material could be jade-like in toughness as well as appearance. When sufficiently compact, cabochons take an excellent polish. The material from Quebec is extremely rare, and transparent crystals are usually tiny.
Pectolite Value
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Pectolite Information
| Data | Value |
| Name | Pectolite |
| Varieties | Larimar |
| Crystallography | Triclinic. Crystals acicular, radial or globular masses; often terminated. |
| Colors | Colorless, white, gray. |
| Luster | Vitreous to silky. |
| Hardness | 4.5-5. |
| Density | 2.74-2.88. |
| Birefringence | 0.036. |
| Cleavage | Perfect 1 direction. Fracture splintery. |
| Stone Sizes | Cabochons up to a few inches have been cut from dense, massive, or fibrous material. A few small faceted gems have been cut from material found at Asbestos, Quebec, about 1973. These are the only known faceted pectolite gems; they range in size up to about 3 carats. |
| Luminescence | In LW, orange-pink (Bergen Hill, New Jersey), cream white (Lendalfoot, Scotland). In SW, greenish yellow (Scotland), yellowish, orange with green areas (Magnet Cove, Arkansas, and Lake County, California), faint yellow with phosphorescence (Paterson, New Jersey). |
| Spectral | Not diagnostic. |
| Formula | NaCa2Si3O8(OH) + Mn. |
Series to Serandite (through Mangan pectolite).
Optics: a=1.595-1.610; β=1.605-1.615; γ=1.632-1.645.
Biaxial (+), 2V= 50-63°. Refractometer spot reading at about 1.60.
Occurrence: In cavities in basaltic rocks, associated with zeolites; in lime-rich metamorphic rocks.
Scotland; Sweden; Czechoslovakia; USSR; Morocco;
South Africa; Japan.
New Jersey; Paterson area, in fine radial sprays: also at Franklin and Sterling Hill.
Alaska: massive, jade-like (used as jade substitute); also fine-grained, pale blue-green.
Lake Count, California; dense material suited for cabochons.
Magnet Cove, Arkansas: pinkish manganiferous material.
Canada: Thetford Mines, Quebec: Asbestos, Quebec: magnificent prismatic crystals, some facetable, also twinned, up to 5 inches long; pale blue-green color, white.
Greenland: manganiferous.
Dominican Republic: compact, white, and various shades of blue (sometimes dark) material capable of cutting cabochons with high polish (larimar).
Comments: Fibrous material has a chatoyancy that gives a catseye effect to cabochons. Pectolite is a curiosity for collectors. The fibrous agregates are seldom cohesive enough to cut, and the material is too soft and fragile for wear, unless the fibers are intergrown. Such material could be jade-like in toughness as well as appearance. When sufficiently compact, cabochons take an excellent polish. The material from Quebec is extremely rare, and transparent crystals are usually tiny.
Dominican pectolite is the loveliest in the world; it is compact and takes a very high polish. It is colored in various shades of blue, and the finest is dark and translucent. The local trade name for the material is Larimar; it and, though locally abundant, this is a rare gem material. The blue color is due to copper.
Name: From the Greek pektos, meaning congealed because of the translucent appearance the mineral sometimes has.
