Rectangle-cut vivianite, 0.95 cts, 8.8 x 4.8, Bolivia. © The Gem Trader. Used with permission.
Vivianite is so fragile and soft, any faceted gems would be difficult to handle safely, let alone wear. Nevertheless, its blue and green colors are so rich, a few stones (very few) have been cut. Vivianites make beautiful collector’s gemstones.
| Data | Value |
|---|---|
| Name | Vivianite |
| Identifying Characteristics | Color darkens in light |
| Formula | Fe3(PO4)2 · 8H2O. |
| Etymology | After J. H. Vivian, the English mineralogist who discovered the species. |
| Occurrence | A secondary mineral in ore veins. Also occurs as an alteration product of primary phosphate minerals in granite pegmatites; forms as sedimentary concretions. |
| Colors | Colorless (fresh); darkens to shades of green and blue, then dark green, dark bluish green, dark purplish, blueish black. |
| Fracture | Fibrous |
| Hardness | 1.5-2 |
| Cleavage | Perfect 1 direction |
| Wearability | Poor |
| Crystallography | Monoclinic. Crystals prismatic, tabular, equant; in clusters, radial groups. Also massive, bladed, fibrous; crusts, earthy masses. |
| Crystallographic Forms | |
| Refractive Index | 1.569-1.675 |
| Birefringence | 0.040-0.059 |
| Dispersion | Weak |
| Luminescence | None |
| Luminescence Present | No |
| Absorption Spectrum | Not diagnostic |
| Pleochroism | Intense: blue/pale yellowish green/pale yellowish green; or deep blue/pale bluish green/pale yellow green; or indigo/yellowish green/yellowish olive-green. |
| Optics | a = 1.569-1.516; β = 1.602-1.656; γ = 1.629-1.675. Biaxial (+) 2V = 63-83°. |
| Optic Sign | Biaxial + |
| Luster | Vitreous, pearly on cleavage; also dull, earthy. |
| Specific Gravity | 2.64-2.68 |
| Transparency | Transparent to opaque |
Three lustrous, deep green vivianites from the Morococala Mine, Santa Fe Mining District, Oruro Department, Bolivia. © Rob Lavinsky, www.iRocks.com. Used with permission.
In an interview, rare-gem faceter and supplier C. D. Parsons acknowledges looking forward to cutting vivianite someday, something very few have done. With a hardness between talc and gypsum (1.5-2) and perfect cleavage, few could manage this feat. Thin pieces are even flexible and sectile (cuttable with a knife). Due to their fragility, vivianites would not make good jewelry stones.
However, this gem material can show beautiful dark shades of blue and green. It also displays intense pleochroism. Depending on the viewing angle, stones can reveal up to three colors, including yellowish green and olive-green, blue-green, and indigo.
When mined, vivianites are colorless or pale green, but their colors darken after exposure to light. As a result, an enthusiast may find an attractive color disappearing over time. Not surprisingly, this further de-incentivizes cutting an already challenging stone. Still, the appeal remains. You’re more likely to find vivianites in mineral collections than jewelry collections.
Vivianite crystal, Huanuni Mine, Huanuni, Dalence Province, Oruro Department, Bolivia. Photo by Géry Parent. Licensed under CC By-SA 3.0.
In the past, vivianite was believed to be the cause of the blue color of so-called odontolite. This fossilized bone and teeth material may resemble turquoise. (It’s also called “bone turquoise”). However, heat treatments have been shown to produce the color artificially.
Like its coloration, vivianite’s streak starts colorless but becomes dark blue over time. Please note: don’t conduct streak testing on finished gems. Test material in inconspicuous spots as a last resort only.
Bolivian material has the following properties.
Scientists have synthesized vivianite for a variety of purposes, including environmental and agricultural research. However, there’s no known jewelry use for this lab-created material. There are no known gemstone treatments or enhancements.
The following sources yield good-quality gem material:
Other notable sources include the following:
An unusual specimen of radiating, intergrown blade-shaped vivianites. Hesse, Germany. © Rob Lavinsky, www.iRocks.com. Used with permission.
Gem cutters rarely facet vivianites, and their almost micaceous cleavage makes polishing gems very difficult. For example, the Bolivian material could yield cut stones up to 75-100 carats. However, this just doesn’t occur.
Store your vivianite specimens out of the light to protect their color. Consult our gemstone jewelry cleaning guide for more recommendations.
Glassy, blue-green vivianites on matrix from Clear Springs Mine, Bartow, Polk County, Florida, USA. © Rob Lavinsky, www.iRocks.com. Used with permission.
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