Chambersite is present in brine returns from a gas storage well on Barber's Hill salt dome, Chambers County, Texas. Crystals are almost colorless to deep purple, paramorphic isometric with the positive tetrahedron as the dominant form. H 7, G 3.49 (meas.), 3.48 (calc.). No cleavage, fracture subconchoidal to uneven. Optically biaxial positive, α = 1.732, β = 1.737, γ = 1.744±0.001, 2V = 83°±3°. Orthorhombic crystal aggregates make up para-morphs. Chemical analysis: MnO 41.87, FeO 1.28, MgO 0.05, CaO tr, B2O3 49.50, Cl 6.34, remainder —1.39. Total 100.43 minus 0=C1 1.39, corrected total 99.04%. The formula is Mn2.90Fe0.09Mg0.01B7O13Cl. Unit cell of the low temperature dimorph is orthorhombic, a = 8.68, b = 8.68, c = 12.26Å; strongest lines of the x-ray powder pattern are (10) 3.07, (6) 2.74, (6) 2.08, (5) 3.54, (5) 2.17. Differential thermal analysis shows the orthorhombic-isometric inversion at 407° C. and melting at 1065° C.

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