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Vivianite (Blue Ochre) [50 g jar] (1.8 oz.)

Item No: 410:200050
Category: 29


Price:  $126.00
Quantity: 





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Description:
Color: Blue Colour Index: Not Listed ASTM Lightfastness: Not tested Hardness: 2 Density: 2.6 Chemical Formula: Fe3+2(PO4)2-8(H2O)

Vivianite, named after the English mineralogist F. G. Vivian, is a rare mineral of secondary origin associated with pyrite in copper and tin veins, and is a hydrated iron phosphate of a blue to green color. It is found principally in two environments: In the oxidized upper layers of ore deposits, where it may appear as dark indigo, blue-black, or green crystals. It is also found in organic rich environments often lining the inside of ancient mollusk shells, but sometimes associated with bones, decaying wood and other organic material. Vivianite forms radiating clusters of acicular (needle-like), prismatic or fibrous bluish-green crystals in association with hematite, siderite or anapaite. Mineral from the latter environment is sometimes collected for use as pigment, but in practice it is more frequently gathered from ore deposits, such as peat bogs and marshy-lakes. Extracting soft, friable vivianite concretions from viscous, dense clayey soil is time-consuming. Once obtained it is necessary to thoroughly wash it to remove clay and organic residue from each grain of vivianite. The labor expended in this operation is rewarded by a high-quality end product. Vivianite is generally stable and dark blue or green in color, though the mineral may be colorless when first exposed. This color transformation is a special feature of vivianite found in peat bogs.
Where Found: At present the most significant reserves of vivianite in Russia are in the Kudinovskoye layer of bog ores near Moscow. Deposits of vivianite are also found in Bolivia; Gervais, Brazil; Colorado, U.S.; Cornwall, England; Crimea, Ukraine; Germany; and Serbia. We obtain our vivianite from bog ore deposits in the Moscow area.
History of Pigment: It exhibits an intense dark blue masstone with a slight reddish blue undertone. Vivianite has rarely been found on European easel paintings, but it has been identified in medieval paintings in Germany and in English medieval polychromy. The School of Cologne used it to depict skies in the 13th and 14th century.
Permanence and Compatibility: Vivianite is recognized to generally be stable, but there have been instances were it was observed to alter from its blue hue to a yellow color. The mineral's color change from colorless to blue on initial exposure is due to increased ferric ion concentrations, and so it has been established that mechanical and chemical processing can produce a change in color.
Oil Absorption and Grinding: Vivianite employed in oil medium has been improperly identified as natural Prussian blue. No data has been published on the oil absorption and grinding qualities of vivianite.
Toxicity: Vivianite is not considered to be toxic, but care should be used in handling the dry powder pigment so as not to inhale the dust.

Read cautions about handling pigments

50 gram bottle
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