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.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
|Crystallography||Monoclinic. Crystals prismatic, tabular, equant; in clusters, radial groups. Also massive, bladed, fibrous; crusts, earthy masses.|
|Refractive Index||1.569 - 1.675|
|Colors||Colorless (fresh); darkens to shades of green and blue, then dark green, dark blueish green, dark purplish, blueish black.|
|Luster||Vitreous, pearly on cleavage; also dull, earthy.|
|Fracture||Fibrous. Thin pieces are flexible and sectile.|
|Specific Gravity||2.64 - 2.68|
|Cleavage||Perfect 1 direction.|
|Transparency||Transparent to Opaque|
|Absorption Spectrum||Not diagnostic.|
|Identifying Characteristics||Color darkens in light.|
|Formula||Fe3(PO4)2 · 8H2O.|
|Pleochroism||Intense: blue/pale yellowish green/pale yellowish green; or deep blue/pale blueish 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°.|
|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.|
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 and perfect cleavage, few could facet this stone. Thin pieces are even flexible and sectile (cuttable with a knife).
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. After exposure to light, their colors darken. 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.
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.
- Refractive indexes: 1.585, 1.603, and 1.639.
- Specific gravity: 2.64.
These sources yield good-quality gem material:
- Bolivia, Llallagua and Poopo: fine, cuttable crystals to 6 inches long.
- Cameroon, N’gaoundere: massive crystals up to 4 feet long, dark in color, cuttable.
- United States: Lemhi County, Idaho, fine crystals; Richmond, Virginia, good crystals; Bingham Canyon, Utah, crystals to 5 inches in length.
Other notable sources include:
- United States: California; Colorado; Delaware; Florida; Maryland; New Jersey; Black Hills, South Dakota (in pegmatites).
- Australia; Canada; England; France; Germany; Japan; Russia.
Gem cutters rarely facet vivianites. 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.
Due to its fragility, this gem material would make an improbable jewelry stone. Store your vivianite specimens out of the light to protect their color. Consult our gemstone jewelry cleaning guide for more recommendations.