Brownleeite: A New Manganese Silicide Mineral in an Interplanetary Dust Particle
Physics and Astronomy
Brownleeite, ideally stoichiometric MnSi, is a manganese silicide not previously observed in nature that was discovered within an interplanetary dust particle that likely originated from a comet. Three submicrometer brownleeite grains were found, with one of them poikilitically enclosed by Mn-bearing forsterite. Owing to the small size of the brownleeite grains, it was not possible to determine conventional macroscopic properties of this mineral; however, the chemical composition and crystal structure were well constrained by extensive quantitative energy dispersive X-ray analysis and electron diffraction using transmission electron microscopy (TEM). The crystal system for brownleeite is cubic (a = 4.557 Å) with space group P213, cell volume = 94.63 Å3, Z = 4, density (calculated) = 2.913 g/cm3, and empirical formula: (Mn0.77Fe0.18Cr0.05)Si. These brownleeite grains likely formed as high-temperature condensates either in the early Solar System or in the outflow of an evolved star or supernova explosion.
K. Nakamura-Messenger, L.P. Keller, S.J. Clemett, S. Messenger, J.H. Jones, R.L. Palma, R.O. Pepin, W. Klöck, M.E. Zolensky, and H. Tatsuoka, 2010. Brownleeite: a New Manganese Silicide Mineral in an Interplanetary Dust Particle. American Mineralogist 95, 221-228.
Publisher's Copyright and Source
Copyright © 2010 American Mineralogist. Article published by American Mineralogist in American Mineralogist, volume 95, issue number 2-3, 2010, pages 221-228. Available online: http://doi.org/10.2138/am.2010.3263.