Larimar and sterling silver ring. Photo courtesy of liveauctioneers.com and Linda Roberts Jewelry.
Fibrous pectolite has long been a curiosity for gem collectors. Compact material can make wonderful cabochons, and transparent crystals are rare and usually tiny. In 1974, blue pectolite was found in the Dominican Republic. Known by the trade name Larimar, this blue gem has since become a popular jewelry stone.
| Data | Value |
|---|---|
| Name | Pectolite (Larimar) |
| Varieties | Larimar |
| Crystallography | Triclinic. Crystals acicular, radial or globular masses; often terminated. |
| Refractive Index | 1.595-1.645 |
| Colors | Colorless, white, gray, pinkish, greenish, purplish. (Larimar can range from dark blue to blue-green and sky blue). |
| Luster | Vitreous to silky |
| Hardness | 4.5-5 (Compact material can reach 6). |
| Fracture | Splintery |
| Specific Gravity | 2.74-2.88 |
| Birefringence | 0.036 |
| Cleavage | Perfect 1 direction |
| Luminescence | See "Identifying Characteristics" below. |
| Luminescence Present | Yes |
| Luminescence Type | Fluorescent, Phosphorescent, UV-Long, UV-Short |
| Transparency | Translucent to transparent. (Opaque to translucent, Larimar) |
| Phenomena | Chatoyancy |
| Formula | NaCa2Si3O8(OH) + Mn. |
| 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. See “Identifying Characteristics” below. |
| Optic Sign | Biaxial + |
| Etymology | From the Greek pektos for “congealed,” because of the mineral's sometimes translucent appearance. Larimar is a combination of Lari, short for “Larissa,” and the Spanish mar for “sea.” Miguel Méndez and Norman Rilling discovered this blue pectolite variety in the Dominican Republic in 1974. Larissa was the name of Méndez's oldest daughter. |
| Occurrence | In cavities in basaltic rocks, associated with zeolites; in lime-rich metamorphic rocks. |
| Inclusions | Hematite can create fern-like “red plume” patterns, calcite crystals. |
Radial growth of white pectolites with pearly luster, 7.0 x 6.3 x 3.4 cm, N’Chwaning Mines, Kuruman, Kalahari manganese fields, Northern Cape Province, South Africa. © Rob Lavinsky, www.iRocks.com. Used with permission.
Although the mineral pectolite occurs in locations across the globe, these fibrous aggregates are seldom cohesive enough to cut and usually too soft and fragile for jewelry wear. However, if pectolite’s fibers grow intertwined, it can become jade-like in toughness as well as appearance.
Pectolite crystals, Jeffrey Pit, Asbestos, Quebec, Canada. © Rob Lavinsky, www.iRocks.com. Used with permission.
With colors ranging from white to various shades of blue, pectolite from the Dominican Republic is the loveliest in the world. Traces of copper contribute to this blue coloration. The finest stones are dark blue and translucent, but sky blue specimens with cloud-like patterns are also highly prized. Known by the trade name Larimar, this variety of compact pectolite can take a very high polish. Though locally abundant, Larimar is a rare gem material.
Pectolites: Larimar cabochons (~ 6 to 30 carats), Dominican Republic. Photo © Joel E. Arem, PhD, FGA. Used with permission.
The minerals pectolite and serandite form a series. Pectolite is the calcium (Ca) end member, while serandite is the manganese (Mn) end member.
The refractive indices (RI) of this series vary with the presence of Ca and Mn.
Chart © Joel E. Arem, PhD, FGA. Used with permission.
Fibrous material has chatoyancy that can give pectolite cabochons a cat’s eye effect.
Larimar cabochon with cat’s eye on a crystal base. Photo by Keyaki. Licensed under CC By-SA 3.0.
In longwave (LW) ultraviolet light:
In shortwave (SW) ultraviolet light:
Although no known pectolite synthetics exist, simulants have surfaced, such as ceramics and “Victoria Stone” and “Imori Stone” glass pieces. However, a gemological analysis can easily identify these.
Some Larimar gems may resemble turquoise or dyed howlite, and other compact pectolites may resemble jade. Again, these can usually be distinguished easily.
German silver earrings with simulated Larimar and quartz stones. Photo courtesy of liveauctioneers.com and Gem & Jewel Craft.
No known common gem treatments.
The Dominican Republic is the principal source of gem-quality pectolite. Larimar is typically cabbed instead of faceted.
Larimar stones from the Filipinas Larimar Mine, Los Checheses, Sierra de Baoruco, Barahona Province, Dominican Republic. Photo by Géry Parent. Licensed under CC By-ND 2.0.
In Canada, the Thetford Mines and Asbestos, Quebec produce magnificent, prismatic crystals. Indeed, these are the only sources of transparent, facetable pectolite, yielding twinned crystals up to 5” long in colors ranging from white to pale blue-green.
Pectolite: Jeffrey Mines, Asbestos, Quebec, Canada (transparent crystals about 1/4” each). Photo © Joel E. Arem, PhD, FGA. Used with permission.
In the United States, Alaska produces massive, jade-like stones (used as jade substitutes) as well as fine-grained, pale blue-green material. Magnet Cove, Arkansas yields pinkish manganiferous material. Lake County, California produces dense material suitable for cabochons. New Jersey has numerous sources, including the Paterson area (fine radial sprays), Bernards Township, Franklin, and Sterling Hill.
Other notable sources include the following locations:
These peachy mauve spheres in this vug are made from thousands of densely packed radial acicular pectolite crystals. 9.6 x 5.9 x 2.9 cm, Millington Quarry, Bernards Township, Somerset Co., New Jersey, USA. © Rob Lavinsky, www.iRocks.com. Used with permission.
Lapidaries have cut cabochons up to a few inches from dense, massive, or fibrous material. Small, faceted gems mined in 1973 from Asbestos, Quebec range in size up about 3 carats, but only a few stones have been faceted.
Although some pectolite stones, especially Larimar, are relatively tough, their hardness range (from 4.5 to 6) makes them susceptible to scratches. Popular jewelry stones, such as quartz, topaz, corundum, and diamond, will scratch them. So, store your pectolite jewelry separately from such pieces. Use protective settings for rings. Pectolite cabs make excellent stones for pendants and earrings.
Clean your gems and jewelry pieces with a soft brush, mild detergent, and warm water. Consult our gemstone jewelry cleaning guide for more recommendations.
Dress ring with larimar cabochon and brilliant-cut diamonds. Photo courtesy of liveauctioneers.com and Fellows.
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