Brokenhillite is a rare mineral that is only found in the far-western regions of

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

in Broken Hill, Australia. Although it has been given a name and chemical formula, it has not been approved by the International Mineralogical Association primarily because it is a

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

silicate of the pyrosmalite group which means the compositional similarities are too great to be an approved mineral. Brokenhillite structure is either composed of

iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...

with the formula . The actual components inside brokenhillite can be determined using a diffractometer. The structural basis of this mineral is determined to be

phyllosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually consid ...

within the pyrosmalites due to the octahedral structure, with one perfect cleavage, a hardness of about 4.5, and a streak of light brown.

Structure

Brokenhillite is a

solid solution A solid solution, a term popularly used for metals, is a homogenous mixture of two different kinds of atoms in solid state and have a single crystal structure. Many examples can be found in metallurgy, geology, and solid-state chemistry. The wor ...

substitution between the end-member elements manganese and iron. The tetrahedral silicates are

inosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually consid ...

s with octahedral dispersal around the islands bonding with oxygen ions. The manganpyrosmalite counterpart has ring silicates forming as 6-fold and bond by manganese-oxygen between the sheets. Ultimately, brokenhillite has broken up disordered stacking due to the inosilicate structure.

Composition

Brokenhillite is mainly manganese dominant with the chemical composition of . Chemically identical to manganpyrosmalite or ferric pyrosmalite, it is thus difficult to distinguish properly. When chloride is present and abundant in the composition it has the potential to become a halide.

Special characteristic

Brokenhillite is found in Broken Hill, New South Wales, Australia in a mine with a wide variety of other minerals present. The hexagonal shape and brown color make it distinguishable especially when a phenomenon called

pleochroism Pleochroism (from Greek πλέων, ''pléōn'', "more" and χρῶμα, ''khrôma'', "color") is an optical phenomenon in which a substance has different colors when observed at different angles, especially with polarized light. Backgrou ...

occurs when light shines through and it becomes translucent white or yellow. The American Mineralogical Association does not approve its classification as a mineral.{{citation needed, date=March 2014

References

* Birch, W. (2007) New South Wales, Australia Its Contribution to Mineralogy, Rocks and Minerals, 82, 1, 40-48. * Mineral Information and Data
"Brokenhillite"
mindat.org. Accessed March 6, 2014. * Mineral Information and Data

mindat.org. Accessed March 6, 2014. * Ozawa, T., Takeuchi, Y., and Takahata, T. (1983) The Pyrosmalite Group Of Minerals. II. The Layer Structure Of McGillite and Friedelite, Canadian Mineralogist, 21, 7-17. * Kato, T., Takeuchi, Y. (1983) The Pyrosmalite Group of Minerals I. Structure Refinement of Manganpyrosmalite, The Canadian Mineralogist Journal of the Mineralogical Association of Canada, 21, 1-6. Inosilicates