Santabarbaraite
Encyclopedia
Santabarbaraite is an amorphous ferric hydroxy phosphate mineral hydrate that was discovered in Tuscany
, Italy
in 2000. It also can be found in Victoria, Australia and Lake Baikal
, Siberia
. This phosphate mineral has a simplified formula Fe3+3(PO4)2(OH)3·5H2O, which is the same formula of another non-amorphous phosphate mineral called allanpringite. Santabarbaraite occurs as pseudomorph
ic masses after vivianite (Fe2+3(PO4)2·8H2O). In the process, monoclinic vivianite oxidizes to form the amorphous santabarbaraite. Pseudomorphism can be seen in Victoria, Australia in Wannon Falls which is originally a well-known locality for vivianite and at Lake Baikal, Siberia where the oxidized santabarbaraite can be seen as a rim surrounding vivianite due to exposure to air.
under ultra violet light. It is also translucent and shows good parting along the cleavage of its original mineral vivianite at {010}. Santabarbaraite's density is 2.24 g/cm3. The mineral is isotropic with refractive index n=1.659.
, the saint of miners
which makes the mineral one of few named after women.
-bearing basin in the Santa Barbara mining district, Tuscany, Italy. Santabarbaraite samples can also be seen in Victoria, Australia underlying Pliocene
basalt
beneath Wannon Falls. It is also found in samples from Lake Baikal, Siberia.
Tuscany
Tuscany is a region in Italy. It has an area of about 23,000 square kilometres and a population of about 3.75 million inhabitants. The regional capital is Florence ....
, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
in 2000. It also can be found in Victoria, Australia and Lake Baikal
Lake Baikal
Lake Baikal is the world's oldest at 30 million years old and deepest lake with an average depth of 744.4 metres.Located in the south of the Russian region of Siberia, between Irkutsk Oblast to the northwest and the Buryat Republic to the southeast, it is the most voluminous freshwater lake in the...
, Siberia
Siberia
Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...
. This phosphate mineral has a simplified formula Fe3+3(PO4)2(OH)3·5H2O, which is the same formula of another non-amorphous phosphate mineral called allanpringite. Santabarbaraite occurs as pseudomorph
Pseudomorph
In mineralogy, a pseudomorph is a mineral or mineral compound that appears in an atypical form , resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is replaced by another...
ic masses after vivianite (Fe2+3(PO4)2·8H2O). In the process, monoclinic vivianite oxidizes to form the amorphous santabarbaraite. Pseudomorphism can be seen in Victoria, Australia in Wannon Falls which is originally a well-known locality for vivianite and at Lake Baikal, Siberia where the oxidized santabarbaraite can be seen as a rim surrounding vivianite due to exposure to air.
Physical properties
Santabarbaraite samples, due to pseudomorphism, show elongated and flattened prism habits. The bulk crystal colour is brown to light brown and but appears yellow brown when viewed in an optical microscope. The mineral's streak colour is also yellow-umber. Santabarbaraite has a vitreous to greasy luster and shows no fluorescenceFluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...
under ultra violet light. It is also translucent and shows good parting along the cleavage of its original mineral vivianite at {010}. Santabarbaraite's density is 2.24 g/cm3. The mineral is isotropic with refractive index n=1.659.
The name
Santabarbaraite is named after the mining district Santa Barbara in Italy where it was found. The name also honors Saint BarbaraSaint Barbara
Saint Barbara, , Feast Day December 4, known in the Eastern Orthodox Church as the Great Martyr Barbara, was an early Christian saint and martyr....
, the saint of miners
Mining
Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...
which makes the mineral one of few named after women.
Geologic occurrence
Santabarbaraite occurs in several places. It occurs in the Valderno Superiore ligniteLignite
Lignite, often referred to as brown coal, or Rosebud coal by Northern Pacific Railroad,is a soft brown fuel with characteristics that put it somewhere between coal and peat...
-bearing basin in the Santa Barbara mining district, Tuscany, Italy. Santabarbaraite samples can also be seen in Victoria, Australia underlying Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
beneath Wannon Falls. It is also found in samples from Lake Baikal, Siberia.
External links
- http://www.mineralatlas.com/mineral%20photos/S/santabarbaraitecp.htm