Bonaccordite

Bonaccordite is a rare mineral discovered in 1974. Its chemical formula is Ni₂FeBO₅ and it is a mineral of the ludwigite group. It usually crystallizes in long, cylindrical prisms that form within another source. It is found as a synthetic mineral in South Africa. It is named after the area of Bon Accord, where it was first found. There have also been findings of bonaccordite within nuclear plants at multiple companies. It builds up a deposit within the machines and is a very hard mineral to clean out because it is resistant to ordinary techniques.

History

Bonaccordite was first described in 1974 for an occurrence in the Bon Accord area, Barberton, Transvaal, South Africa.[1] It occurs in a tabular nickeliferous serpentinite, on the margin of an ultramafic intrusive.[1] The actual site of the bonaccordite finding is a possible meteorite site three kilometers west of the Scotia talc mine.[2]

Composition

The chemical formula for bonaccordite is Ni₂FeBO₅.[3]

Table 1. Chemical data of bonaccordite^[3]
Fe₂O	31.9%
NiO	52.7%
MgO	0.5%
MnO	0.04%
CaO	1.5%
SiO₂	0.4%
B₂O₃	13.1%
Total	100.44%

The two analysts confirmed the presence of boron by using the wet-chemical analysis. The full mineral formula is Ni_1.86Co_0.05Mg_0.03MN_0.002Si_0.02Fe_1.05B_0.99O_0.5.[3] The molecular weight is 264.03 grams.

Geologic occurrence

According to De Waal, Viljoen, and Calk (1974), bonaccordite can occur as either a cluster of thin, long prisms or rosette-like radiating groups. The prisms can form veins through other minerals and the radiating groups can occur in minerals like liebenbergite or trevorite.[3] Bonaccordite usually occurs along with trevorite, liebenbergite, népouite, nimite, gaspeitev, and millerite in the area of Bon Accord.[4] All of these minerals crystallize as slender prisms.

Physical properties

Bonaccordite is an opaque mineral with a reddish brown color.[3] In reflected light, the color is grey with a brownish tinge with strong reddish brown internal reflections.[3] In many cases, bonaccordite crystallizes into long, slender cylinders.[5] It has been discovered to be the nickel analogue of ludwigite.[3]

The Mohs hardness for bonaccordite is 7 and its density is 5.17 g/cm3.[5] The optical class is biaxial.[2] The space group has been determined as [Pbam] and cell dimensions were calculated to a = 9.213(6) b = 12.229(7) c = 3.001(2) Z = 4.[2] Bonaccordite is insoluble and has only shown reactivity to hydrochloric acid. It is a very tough mineral and is extremely hard to clean it off of nuclear plant machines.[6]

Bonaccordite has an orthorhombic crystal system with a point group of 2/m 2/m 2/m. The crystals are structured as elongated prisms within another material.[2] There has been no observed cleavages or twinning.

References

1. ^ a b http://webmineral.com/data/Bonaccordite.shtml Webmineral data
2. ^ a b c d http://rruff.geo.arizona.edu/doclib/hom/bonaccordite.pdf Anthony, J.W., Bideaux, R., Bladh, K., & Nichols, M. (2003) Bonaccordite Ni2FeBO5. Handbook of Mineralogy. Mineral Data Publishing.
3. ^ a b c d e f g 2. De Waal S.A., Viljoen E.A., Calk L.C. (1974) Nickel Minerals form Barberton, South Africa: VII Bonaccordite. The Nickel Analogue of Ludwigite. Transactions of the Geological Society of South Africa. 77, p 375.
4. ^ 4. Fleischer M., Cabri L. (1976) New Mineral Names. American Mineralogist. 61, P 502-504.
5. ^ a b 5. Sawicki Jerry. (2008) Evidence of Ni2Ni2FeBO55 and m-ZrO₂ precipitates in fuel rod deposits in AOA-affected high boiling duty PWR core. Journal of Nuclear Materials. 374, p 248-269.
6. ^ 3. Deshon J. (2003) Advisory Committee on Reactor Safeguards Reactor Fuels Subcommittee - Open Session. United States of America Nuclear Regulatory Committee.

External links

* mindat.org entry
* webmineral.com entry

List of minerals

Minerals Images