Jarosewichite is a rare manganese

Manganese

Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...

 arsenate mineral

Arsenate mineral

Arsenate minerals usually refer to the naturally occurring orthoarsenates, possessing the 3- anion group and, more rarely, other arsenates with anions like AsO32- or [AsO22]- . Arsenite minerals are much less common...

 with formula: Mn²⁺₃Mn³⁺(AsO₄)(OH)₆. It was first described in Franklin, New Jersey

Franklin, New Jersey

Franklin is a Borough in Sussex County, New Jersey, United States. As of the 2010 United States Census, the borough population was 5,045.Franklin, known as the "Fluorescent Mineral Capital of the World," is located over a rich ore body containing more than 150 minerals, many of them fluorescent and...

 which is its only reported occurrence. Its chemical composition and structure are similar to chlorophoenicite. This mineral is orthorhombic with 2/m2/m2/m point group. Its crystals are prismatic or barrel-shaped. The color of jarosewichite is dark red to black. It has subvitreous luster of fracture surfaces and reddish orange streak. This mineral occurs with flinkite, franklinite

Franklinite

Franklinite is a mineral with formula ZnFe2O4. It is associated with the Franklin Mine and Sterling Hill Mines in New Jersey.-See also:* Spinel* Classification of minerals* List of minerals-References:*...

, andradite

Andradite

Andradite is a species of the garnet group. It is a nesosilicate, with formula Ca3Fe2Si3O12.Andradite includes three varieties:* Melanite: Black in color, referred to as "titanian andradite"....

 and cahnite

Cahnite

Cahnite is a brittle white or colorless mineral that has perfect cleavage and is usually transparent. It usually forms tetragonal-shaped crystals and it has a hardness of 3 mohs. Cahnite was discovered in the year 1921. It was named Cahnite to honor Lazard Cahn, who was a mineral collector and...

.

Composition

The chemical composition of jarosewichite was obtained in 1982. These data were obtained by electron microprobe analysis with a voltage of 15 kV and a current of 0.025μA. Manganite(Mn), synthetic olivenite(As), synthetic ZnO(Zn), and hornblende(Ca, Mg, Fe) are used as standards for the analysis. Water percentage of the sample cannot be measured directly because of lacking large size of sample. The composition of jarosewichite is as follows:

• As₂O₅ 24.0
• Mn₂O₃ 17.7
• FeO 0.4
• MnO 42.3
• ZnO 1.2
• MgO 2.1
• CaO 0.2
• H₂O 12.1
• Total 100.0

The final calculation formula of unit cell contents is :
[Mn³⁺_1.00(Mn²⁺_2.74Mg_0.24Fe_0.03Ca_0.02Zn_0.07)_∑3.10(AsO₄)_0.95(OH)_6.35], with Z=8
This result is very similar to the theoretical formula, which is Mn²⁺₃Mn³⁺(AsO₄)(OH)₆. The theoretical weight percent of oxides are: Mn₂O₃=17.14, MnO=46.20, As₂O₅=24.95 and H₂O=11.71, and the sum is 100.

Structure

Jarosewichite is orthorhombic crystal, and the space group is C2/m2/m2/m. The three axes are a=6.56(3), b=25.20(10) and c=10.00(5). These results are from the d-values measurement of a jarosewichite powder, all reflection with odd h or k are very weak, so they are not used to determine the powder pattern.

Physical properties

The color of jarosewichite in nature is very dark red, sometimes black. It has subvitreous luster of fracture surfaces and reddish orange streak

Streak (mineralogy)

The streak of a mineral is the color of the powder produced when it is dragged across an unweathered surface. Unlike the apparent color of a mineral, which for most minerals can vary considerably, the trail of finely ground powder generally has a more consistent characteristic color, and is thus...

. The Mohs scale of hardness is almost 4. The density is 3.66(4) g/cm³, which is determined by heavy liquid techniques. This value is very similar to the calculated result of 3.70 g/cm³.

In optical aspect, jarosewichite is biaxial and its refractive indices are α=1.780(5),β=1.795(5) and γ=1.805(5). The calculated value of 2V is 78°. The determination of refractive index and 2V has high standard errors, because the refractive index can be influenced by liquids and the crystal size is very small.

Geologic occurrence

Jarosewichite was first found by David K. Cook in Franklin, Sussex County, New Jersey. It always occurs with flinkite, franklinite, andradite and cahnite. The mine specimen has a stratified crust of vugs from metamorphosed zinc orebody. There are some small crystals of hausmannite

Hausmannite

Hausmannite is a complex oxide of manganese containing both di- and tri-valent manganese. The formula can be represented as Mn2+Mn3+2O4. It belongs to the spinel group and forms tetragonal crystals...

, allactite

Allactite

Allactite is a rare arsenate mineral of metamorphosed manganese zinc ore deposits. It is found in Sweden and New Jersey, USA. Its name originated from Greek αλλάκτειν meaning "to change", referring to the strong pleochroism of the mineral....

 and cahnite

Cahnite

Cahnite is a brittle white or colorless mineral that has perfect cleavage and is usually transparent. It usually forms tetragonal-shaped crystals and it has a hardness of 3 mohs. Cahnite was discovered in the year 1921. It was named Cahnite to honor Lazard Cahn, who was a mineral collector and...

 on the vugs, which formed with jarosewichite.

Special characteristics

Jarosewichite has high content of manganese, which was used in coins. During the Second World War, the nickel coin in America was made of an alloy of copper, silver and manganese instead of copper and nickel, which was shortage in the special time . The element of arsenic in this mineral is widely used in agricultural as insecticide.

Biographic sketch

Jarosewichite was named in honor of Eugene Jarosewich

Eugene Jarosewich

Eugene Jarosewich was a chemist in the Department of Mineral Sciences at the Smithsonian Institution. Gene was known worldwide for his wet chemical analyses of meteorites...

 (1926–2007), a chemist in the Department of Mineral Sciences of Smithsonian Institution

Smithsonian Institution

The Smithsonian Institution is an educational and research institute and associated museum complex, administered and funded by the government of the United States and by funds from its endowment, contributions, and profits from its retail operations, concessions, licensing activities, and magazines...

, Washington, D.C., USA. Gene was known in the instrumental analysis of rocks and minerals, especially in wet chemical analyses of meteorites. In the 1970s, Gene and his co-workers also established a set of analytical standards of electron microprobe.
The asteroid 4320 Jarosewich(1981 EJ17) was also named after Eugene Jarosewich.

Literature survey

This mineral was first mentioned by Cook’s ”Recent work on the minerals of Franklin and Sterling Hill, New Jersey”(1973). But Cook did not recognize that it was a new mineral, he described it as carminite. The first article described it as jarosewichite is Dunn’s “Jarosewichite and a related phase: basic manganese arsenates of the chlorophoenicite group from Franklin, New Jersey”(1982). This article is also the most highly cited paper in Web of Science with five citations and it provided the accurate composition of jarosewichite. The structure of jarosewichite is very similar to chlorophoenicite, so Moore’s “The crystal structure of chlorophoenicite ”(1968) is also helpful to this research. Anthony and other 3 writer’s “Handbook of Mineralogy”(2001) provided comprehensive basic information of jarosewichite, but their research is not deep.