Lawsonbauerite, (Mn,Mg)5Zn2(SO4)(OH)12 · 4H2O, is a new mineral found in the Sterling Hill mine, Ogdensburg, Sussex County, New Jersey. Lawsonbauerite is monoclinic, P21/c with a = 10.54(5), b = 9.62(5), c = 16.46(8)A, β = 95.21(10)°, Z = 4. The strongest reflections in the X-ray diffraction pattern are (d in A, intensity, hkl) 10.5 100 100; 5.24 60 200; 3.90 50 122; 1.587 50 hkl?.

Lawsonbauerite is colorless to white, but most crystals have an amorphous black coating. The Mohs hardness is approximately 4½ The density is 2.87 g/cm3 (meas), 2.92 g/cm3 (calc). There is no cleavage and no response to ultraviolet radiation. Optically, lawsonbauerite is biaxial (–) with refractive indices α = 1.590, β = 1.608, γ = 1.611; 2 Vx = 42° (meas), 45 (calc). Dispersion is strong, r > v. The orientation is Y parallel to b, c Λ Z = 7°in the acute angle between a and c.

The composition of lawsonbauerite, determined by electron microprobe, is MgO 8.4, MnO 32.6, FeO 0.1, ZnO 23.1, SO3 10.8 percent, with H2O 25.0 percent by difference. The ideal formula is (Mn,Mg)5Zn2(SO4)(OH)12 · 4H2O. Lawsonbauerite is known only from Sterling Hill and is associated with pyrochroite, zincite, and sussexite.

Lawsonbauerite is the manganese analog of torreyite, which has the ideal composition (Mg,Mn)5Zn2(SO4)(OH)12 · 4H2O. New data are given for torreyite, confirming the relationship to lawsonbauerite. Lawsonbauerite is named in honor of Lawson H. Bauer (1889-1954), chief chemist for the New Jersey Zinc Company and describer of torreyite.

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