Lawsonbauerite, a new mineral from the Sterling Hill Mine, New Jersey, and new data for torreyite

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 V_x = 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.