Bonaccordite
Encyclopedia
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 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.
, Transvaal
, South Africa. It occurs in a tabular nickeliferous serpentinite
, on the margin of an ultramafic intrusive. The actual site of the bonaccordite finding is a possible meteorite
site three kilometers west of the Scotia talc mine.
The two analysts confirmed the presence of boron by using the wet-chemical analysis.
. Bonaccordite usually occurs along with trevorite, liebenbergite, népouite
, nimite, gaspeitev, and millerite
in the area of Bon Accord. All of these minerals crystallize as slender prisms.
.
The Mohs hardness for bonaccordite is 7 and its density is 5.17 g/cm3. The optical class is biaxial. 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. 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 and has only shown reactivity to hydrochloric acid
. It is very hard to clean it off of fuel rods in nuclear power reactors where it is sometimes formed.
It has been shown to form hydrothermally in near-supercritical water at temperatures above 350oC and in presence of alkaline conditions. 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.
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 vonsenite and szaibelyite...
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, BarbertonBarberton, Mpumalanga
Barberton is a town in the Mpumalanga province of South Africa, which has its origin in the 1880s gold rush in the region. It is situated in the De Kaap Valley and is fringed by the Mkhonjwa Mountains...
, Transvaal
Transvaal Province
Transvaal Province was a province of the Union of South Africa from 1910 to 1961, and of its successor, the Republic of South Africa, from 1961 until the end of apartheid in 1994 when a new constitution subdivided it.-History:...
, South Africa. It occurs in a tabular nickeliferous serpentinite
Serpentinite
Serpentinite is a rock composed of one or more serpentine group minerals. Minerals in this group are formed by serpentinization, a hydration and metamorphic transformation of ultramafic rock from the Earth's mantle...
, on the margin of an ultramafic intrusive. The actual site of the bonaccordite finding is a possible meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
site three kilometers west of the Scotia talc mine.
Composition
The chemical formula for bonaccordite is Ni2FeBO5.| Table 1. Chemical data of bonaccordite | |
|---|---|
| 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.
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 trevoriteTrevorite
Trevorite is a very rare nickeliferous 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 insoluble in most acids.There is at least partial solid...
. Bonaccordite usually occurs along with trevorite, liebenbergite, népouite
Népouite
Népouite is a rare nickel silicate mineral which has the apple green colour typical of such compounds. It was named by E Glasser in 1907 after the place where it was first described , the Népoui Mine, Népoui, Nouméa Commune, Northern Province, New Caledonia...
, nimite, gaspeitev, and millerite
Millerite
Millerite is a nickel sulfide mineral, NiS. It is brassy in colour and has an acicular habit, often forming radiating masses and furry aggregates...
in the area of Bon Accord. 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 ludwigiteLudwigite
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 vonsenite and szaibelyite...
.
The Mohs hardness for bonaccordite is 7 and its density is 5.17 g/cm3. The optical class is biaxial. Bonaccordite has an orthorhombic crystal system with a point group
Point group
In geometry, a point group is a group of geometric symmetries that keep at least one point fixed. Point groups can exist in a Euclidean space with any dimension, and every point group in dimension d is a subgroup of the orthogonal group O...
of 2/m 2/m 2/m. The crystals are structured as elongated prisms within another material. There has been no observed cleavages
Cleavage (crystal)
Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite crystallographic structural planes. These planes of relative weakness are a result of the regular locations of atoms and ions in the crystal, which create smooth repeating surfaces that are visible both in the...
or twinning
Crystal twinning
Crystal twinning occurs when two separate crystals share some of the same crystal lattice points in a symmetrical manner. The result is an intergrowth of two separate crystals in a variety of specific configurations. A twin boundary or composition surface separates the two crystals....
. 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 and has only shown reactivity to hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
. It is very hard to clean it off of fuel rods in nuclear power reactors where it is sometimes formed.
It has been shown to form hydrothermally in near-supercritical water at temperatures above 350oC and in presence of alkaline conditions. 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.