Bonaccordite is a rare mineral discovered in 1974. Its chemical formula is Ni₂FeBO₅ and it is a mineral of the

ludwigite Ludwigite is a magnesium-iron borate mineral: Mg2FeBO5. Ludwigite typically occurs in magnesian iron skarn and other high temperature contact metamorphic deposits. It occurs in association with magnetite, forsterite, clinohumite and the borates ...

group. It usually crystallizes in long, cylindrical prisms that form within another source. 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 Transvaal is a historical geographic term associated with land north of (''i.e.'', beyond) the Vaal River in South Africa. A number of states and administrative divisions have carried the name Transvaal. * South African Republic (1856–1902; af, ...

, South Africa.Webmineral data
/ref> It occurs in a tabular nickeliferous

serpentinite Serpentinite is a rock composed predominantly of one or more serpentine group minerals, the name originating from the similarity of the texture of the rock to that of the skin of a snake. Serpentinite has been called ''serpentine'' or ''ser ...

, on the margin of an

ultramafic Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed ...

intrusive. The actual site of the bonaccordite finding is a possible

meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the ...

site three kilometers west of the Scotia talc mine.Handbook of Mineralogy
/ref>

Composition

The chemical formula for bonaccordite is Ni₂FeBO₅. The two analysts confirmed the presence of boron by using wet-chemical analysis.

Geologic occurrence

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 Trevorite is a rare nickel iron oxide mineral belonging to the spinel group. It has the chemical formula NiFe3+2O4. It is a black mineral with the typical spinel properties of crystallising in the cubic system, black streaked, infusible and insolu ...

.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 Bonaccordite usually occurs along with trevorite, liebenbergite,

népouite Népouite is a rare nickel silicate mineral which has the apple green colour typical of such compounds. It was named by the French mining engineer Edouard Glasser in 1907 after the place where it was first described (the type locality), the Nép ...

, nimite, gaspeitev, and

millerite Millerite is a nickel sulfide mineral, Ni S. It is brassy in colour and has an acicular habit, often forming radiating masses and furry aggregates. It can be distinguished from pentlandite by crystal habit, its duller colour, and general l ...

in the area of Bon Accord.Fleischer M., Cabri L. (1976) New Mineral Names. American Mineralogist. 61, P 502-504. All of these minerals crystallize as slender prisms.

Physical properties

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

. The

Mohs hardness The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by th ...

for bonaccordite is 7 and its density is 5.17 g/cm³. The optical class is

biaxial In crystal optics, the index ellipsoid (also known as the ''optical indicatrix'' or sometimes as the ''dielectric ellipsoid'') is a geometric construction which concisely represents the refractive index, refractive indices and as ...

. Bonaccordite has an

orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a r ...

crystal system with a

point group In geometry, a point group is a mathematical group of symmetry operations (isometries in a Euclidean space) that have a fixed point in common. The coordinate origin of the Euclidean space is conventionally taken to be a fixed point, and every p ...

of 2/m 2/m 2/m. The crystals are structured as elongated prisms within another material. There has been no observed cleavages or twinning. 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. Bonaccordite is

insoluble In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubil ...

and has only shown reactivity to

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...

. It is very hard to clean it off of fuel rods in nuclear power reactors where it is sometimes formed.Deshon J. (2003) Advisory Committee on Reactor Safeguards Reactor Fuels Subcommittee - Open Session. United States of America Nuclear Regulatory Committee.Sawicki J.A. (2008) Evidence of Ni₂FeBO₅ and m-ZrO₂ precipitates in fuel rod deposits in AOA-affected high boiling duty PWR core. Journal of Nuclear Materials. 374, p 248-269. It has been shown to form hydrothermally in near-supercritical water at temperatures above 350 °C and in presence of alkaline conditions.Sawicki J.A. (2011) Hydrothermal synthesis of Ni₂FeBO₅ in near-supercritical PWR coolant and possible effects of neutron-induced 10^B fission in fuel crud. Journal of Nuclear Materials. 415, p 179-188. Zs Rak, CJ O'Brien, Dongwon Shin, Anders David Andersson, CR Stanek, DW Brenner (2016) Theoretical assessment of bonaccordite formation in pressurized water reactors. Journal of Nuclear Materials, 474, p. 62-64. Its formation in PWR reactors can be accelerated by lithium produced in ¹⁰B(n,α)⁷Li reaction with boron in coolant. Bonaccordite can be an indicator of Axial-Offset-Anomaly of neutron flux and power density in PWR power plants.

References

{{Reflist Nickel minerals Iron(III) minerals Borate minerals Orthorhombic minerals Minerals in space group 55 Minerals described in 1974