Lindsleyite (Ba) and mathiasite (K): two new chromium-titanates in the crichtonite series from the upper mantle.
Article
Haggerty, SE, Smyth, JR, Erlank, AJ et al. (1983). Lindsleyite (Ba) and mathiasite (K): two new chromium-titanates in the crichtonite series from the upper mantle.
. AMERICAN MINERALOGIST, 68(5-6), 494-505.
Haggerty, SE, Smyth, JR, Erlank, AJ et al. (1983). Lindsleyite (Ba) and mathiasite (K): two new chromium-titanates in the crichtonite series from the upper mantle.
. AMERICAN MINERALOGIST, 68(5-6), 494-505.
Lindsleyite and mathiasite are, respectively, the Ba and K members of the series AM21O38, characterized by predominant A-specific, large cations and by M-formula small cations. Typical analyses yielded the following compositions: for lindsleyite, A = Ba0.62Sr0.41Ca0.09Pb0.01K0.07-Na0.06REE0.03, M = Ti11.63Zr0.87Al0.11Cr3.89Fe2.87Mg1.49Nb0.08; for mathiasite, A = K0.66Ca0.22Sr0.15Ba0.10Na0.05REE0.05, M = Ti13.18Zr0.62- Cr2.87Fe2.28Mg1.63Ca0.22Nb0.09. Macroscopically resembling ilmenite and rutile, both new minerals are black and opaque with metallic lustre and conchoidal fracture. They are distinguished from ilmenite and rutile in reflected light by their pale tan colour and weaker pleochroism and anisotropy (spectral reflectance data, also similar to ilmenite and rutile, are tabulated.) Both lindsleyite and mathiasite are hexagonal, space group R3 or R3, with lattice parameters, densities and strongest powder XRD lines as follows: for lindsleyite, a 1.037, c 2.052 nm; Dcalc. 4.63 g/cm3; 2.13, 1.80, 1.59 and 1.44 A (all 100); for mathiasite, a 1.035, c 2.058 nm; Dcalc. 4.60 g/cm3; 2.14(100), 1.44(100) and 2.25(90) A. These new minerals were found in association with K-richterite, phlogopite, Nb-Cr-rutile and Nb-Cr-Mg-ilmenite from metasomatized peridotites and heavy media concentrates from 4 kimberlites in the Republic of South Africa. They appear to have formed by metasomatizing fluids enriched in K, Ba, REE and Ti. The names are for Professors Donald H. Lindsley and Morna Mathias.
