Baotite is a rare mineral with the chemical formula Ba4Ti4(Ti, Nb, Fe)4(Si4O12)O16Cl, recognized as having a unique four-fold silicate ring.Chakhmouradian, A.R. and Mitchell, R.H. (2002) The mineralogy of Ba- and Zr-rich alkaline pegmatites from Gordon Butte, Crazy Mountains (Montana, USA): comparisons between potassic and sodic agpaitic pegmatites. Contributions to Mineralogy and Petrography, 143, 93-114. Crystals are tetragonal, though commonly deformed to the extent of appearing monoclinic. Named for the locality of first discovery, Baotou, China, baotite has been found in hydrothermal veins and alkalic rocks in various locations around the world.
Structure Simonov first determined the crystal structure of baotite in which (Ti, Nb, Fe)-octahedra share edges, forming chains and cross-linking at the corners forming a 4-fold screw axis in the (001); these columns are analogous to those in rutile.Simonov, V.I. (1960) Baotite, a mineral with a metasillicate ring (Si4O12). Kristallografiya, 5, 544-546 (in Russian). Abs. in American Mineralogist, 46, 466, 1961. Four silicate tetrahedra share corners creating characteristic rings in the plane perpendicular to the c axis.Shinno, I. and Li, Z. (1998) Mössbauer studies of baotite and bafertisite. Hyperfine Interactions, 116, 189-196. The barium cation is between the rings and rutile columns, while chloride fills the void between each pair of rings.Cooper, A.F. (1996) Nb-rich baotite in carbonatites and fenites at Haast River, New Zealand. Mineralogical Magazine, 60, 473-482. Chlorine's presence is not necessary for the structure to balance electrostatically.
Geologic occurrence The first sample of baotite was found with galena, pyrite, albite, aegirine and alkali amphiboles in a quartz vein cutting quartzitePeng, C.J. (1959) The discovery of several new minerals of rare elements. Ti-Chin Ko-hsuch, 10 (in Chinese). Abs. in American Mineralogist, 45, 754, 1960. at the Bayan Obo Mine in China. Grains from Ravalli County, Montana were found in a thin calcite crust on masses of eschynite within a carbonatic vein.Heinrich, E.W., Boyer, W.H. and Crowley, F.A. (1962) Baotite (Pou-t’ou-k’uang) from Ravalli County, Montana. American Mineralogist, 47, 987-993. Baotite also occurs at Haast River, New Zealand as an accessory phase of carbonatite, fenite and hydrothermal fluid veins associated with a dike swarm. The dike intrusion of mantle-derived magmas can likely be attributed to the close proximity of the Alpine fault plate boundary across South Island, New Zealand.
References
External links Fact sheet from Mindat.org Fact sheet from Webmineral.com