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Gemstones 250x250

The Mineral vivianite

Doubly Terminated Matrix Vivanite

Vivianite is a well-known phosphate mineral, forming in highly aesthetic sharply colored crystals. Vivianite often forms with organic material such as shells and fossils, and may even form inside them.

Vivianite is notorious for darkening upon exposure to light. This is caused by a chemical transformation of the iron which is responsible for its color deepening and decrease of transparency. Continued exposure may eventually turn a specimen black and make it completely opaque. Certain specimens may also be unstable and form cracks along cleavage surfaces when exposed to light. Due to its instability, it is recommended to keep all Vivianite specimens covered and out of any light except for the short periods of time when it is being looked at.

Vivianite is named in honor of John Henry Vivian (1785 - 1855), an English mineralogist and mine owner who first discovered this mineral in Cornwall.

Chemical Formula

Fe3(PO4)2 · 8(H2O)

Color

Green to dark green, greenish-blue, blue, indigo-blue, grayish-blue, black; rarely purple or multicolored.

Crystal System

Monoclinic

Properties

Streak
White; turns greenish-blue to blue upon exposure to light.
Hardness
1.5 - 2
Transparency
Transparent to opaque
Specific Gravity
2.6 - 2.7
Luster
Vitreous to dull. Pearly on cleaved surfaces.
Cleavage
1,1
Fracture
Splintery
Tenacity
Sectile and slightly flexible
Other ID Marks
Color often darkens upon prolonged exposure to light.

Crystal Habits

In short to long prismatic crystals, usually thin and bladed. Also tabular, micaceous, radiating, , fibrous, coxcomb, concretionary, nodular, and earthy. Crystals may have growth layers and elongated crystals may be bent.

3D Crystal Atlas

Additional Information

Composition
Hydrous iron phosphate
In Group
Phosphates; True Phosphates
Striking Features
Color, crystal habits, and streak.
Environment
Vivianite occurs in multiple environments, especially organically-rich sedimentary deposits such as clays and sandstones. It also occurs in hydrothermal replacement deposits and in phosphate-rich granite pegmatites.
Rock Type
Igneous, Sedimentary, Metamorphic

Varieties

 -   Vivianite from Mullica Hill, New Jersey

Uses

Good crystals and sprays of Viviante make an important and expensive collectors material.

Noteworthy Localities

Bolivia has provided the collector with the world's finest examples of Vivianite. The fines Bolivian Vivianites are in transparent gemmy dark green crystals with distinct sharply angled terminations. Specific Bolivian localities include the Tomokoni mine, Machacamarca District (Colavi), Potosí; the Siglo Veinte Mine, Llallagua, Potosí; and the Morococala and Huanani Mines, Dalence, Oruro.

The Kerch peninsula, Crimea, Ukraine, is well known for exceptional Vivianite crystal sprays in fossilized shells. Sharp dark coxcomb balls came Berstadt, Wetterau, Hesse, Germany. Dark transparent green Vivianite crystal clusters come from several pegmatites in Minas Gerais, Brazil, especially Cigana, Conselheiro Pena, in the Doce valley. In Mexico, sharp crystals came from Santa Eulalia, Chihuahua.

In the U.S., large Vivianite crystals, including a rare violet and multicolored variety, came from the Blackbird District, Lemhi Co., Idaho. An old classic locality is Leadville, Lake Co., Colorado; as well as a built-over area in downtown Richmond, Henrico Co., Virginia. Vivianite associated with organic material comes from Mullica Hill, Gloucester Co., New Jersey; and light blue microcrystals come from the Palermo No. 1 Mine, Groton, Grafton Co., New Hampshire.

Common Mineral Associations

Quartz, Limonite, Siderite, Goethite, Muscovite, Sphalerite, Ludlamite

Distingushing Similar Minerals

Vivianite is is not easily confused with other minerals. The micas and Chlorite may have similar properties but often form in different crystal habits.


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