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Hydroxylpyromorphite, Pb5(PO4)3(OH), has been documented in the literature as a synthetic and naturally occurring phase for some time but has not previously been formally described as a mineral. It is fully described here for the first time using crystals collected underground in the Copps mine, Gogebic County, Michigan. Hydroxylpyromorphite occurs as aggregates of randomly oriented hexagonal prisms, primarily between about 20-35 µm in length and 6-10 µm in diameter. The mineral is colorless and translucent with vitreous luster and white streak. The Mohs hardness is ~3 1/2-4; the tenacity is brittle, the fracture is irregular, and indistinct cleavage was observed on {001}. Electron microprobe analyses provided the empirical formula Pb4.97(PO4)3(OH0.69 F0.33Cl0.06)Σ1.08. The calculated density using the measured composition is 7.32 g/cm³. Powder X-ray diffraction data for the type material is compared to data previously reported for hydroxylpyromorphite from the talc mine at Rabenwald, Austria, and from Whytes Cleuch, Wanlockhead, Scotland. Hydroxylpyromorphite is hexagonal, P63/m, at 100 K, a = 9.7872(14), c = 7.3070(10) Å, V = 606.16(19) ų, and Z = 2. The structure [R1 = 0.0181 for 494 F>4σ(F) reflections] reveals that hydroxylpyromorphite adopts a column anion arrangement distinct from other members of the apatite supergroup due to the presence of fluorine and steric constraints imposed by stereoactive lone-pair electrons of Pb2+ cations. The F- anion sites are displaced slightly from hydroxyl oxygen anions, which allows for stronger hydrogen-bonding interactions that may in turn stabilize the observed column-anion arrangement and overall structure. Our modern characterization of hydroxylpyromorphite provides deeper understanding to a mineral useful for remediation of lead-contaminated water. [ABSTRACT FROM AUTHOR]

The new minerals carlsonite (IMA2014-067), (NH4)5Fe33+O(SO4)6⋅7H2O, and huizingite-(Al) (IMA2015-014), (NH4)9Al3(SO4)8(OH)2⋅4H2O, formed from a natural fire in an oil-bearing shale near Milan, Ohio. Carlsonite crystals are yellow to orange-brown thick tablets, flattened on {001}, or stout prisms, elongated on [110], up to about 0.5 mm in size. The mineral has a tan streak, vitreous luster, Mohs hardness of 2, brittle tenacity, irregular fracture, perfect {001} cleavage, calculated density of 2.167 g/cm³, and is easily soluble in H2O. Carlsonite is optically biaxial (-), α = 1.576(1), β = 1.585(1), and γ = 1.591(1) (white light). Huizingite-(Al) crystals, typically intergrown in light greenish yellow drusy aggregates, are tabular to bladed, flattened on {100}, up to about 0.25 mm in maximum dimension. The mineral has a white streak, vitreous luster, Mohs hardness of 2%, brittle tenacity, irregular fracture, no cleavage, calculated density of 2.026 g/cm³, and is easily soluble in H2O. Huizingite-(Al) is optically biaxial (+) with α = 1.543(1), β = 1.545(1), and γ = 1.563(1) (589.6 nm light). Raman and infrared spectroscopy was conducted on both minerals. Electron microprobe analyses provided the empirical formulas [(NH4)4.64Na0.24K0.12]Σ5.00Fe3.053+O(SO4)6⋅6.93H2O and [NH4)8.76Na0.22K0.02]Σ9.00(Al1.65Fe1.343+) Σ2.99 (OH)1.98(H2O)4.02(SO4)8.00 for carlsonite and huizingite-(Al), respectively. Huizingite compositions with Fe > Al were noted. Carlsonite is triclinic, P1, a = 9.5927(2), b = 9.7679(3), c = 18.3995(13) Å, α = 93.250(7)°, β = 95.258(7)°, g = 117.993(8)°, V = 1506.15(16) ų, and Z = 2. Huizingite-(Al) is triclinic, PT, a = 9.7093(3), b = 10.4341(3), c = 10.7027(8) Å, α = 77.231(5)°, β = 74.860(5)°, γ = 66.104(5)°, V= 948.73(9) ų, and Z = 1. The five strongest lines in the X-ray powder diffraction pattern of carlsonite are [dobs in Å(I) (hkl)]: 9.23(100)(002); 8.26(40)(100,011); 7.57(43)(111,111,011); 4.93(23)(1 11,120); and 3.144(41)(multiple). Those for huizingite-(Al) are: 8.82(60)(100); 5.04(69)(121); 3.427(100)(2 21); 3.204(68)(211); and 3.043(94)(212,312). The crystal structures of carlsonite (R1 = 0.030) and huizingite (R1 = 0.040) are bipartite, each consisting of a structural unit and an interstitial unit. For carlsonite, the structural unit is a [Fe33+O(H2O)3(SO4)6]5- cluster and the interstitial complex is [(NH4)5(H2O)4]5+. For huizingite-(Al), the structural unit is a [(Al,Fe3+)3(OH)2(H2O)4(SO4)6]5- cluster and the interstitial complex is [(NH4)9(SO4)2]5+. In the carlsonite cluster, three FeO6 octahedra share a common vertex, while in the huizingite-(Al) cluster, three (Al,Fe)O6 octahedra form an abbreviated corner-linked chain. The cluster in carlsonite is the same as that in metavoltine, while the huizingite-(Al) cluster is unique. The range ofLewis basicity of the structural unit in carlsonite is 0.23-0.11 valence units (v.u.) and in huizingite-(Al) it is 0.20-0.12 v.u.; the corresponding Lewis acidities of the interstitial complexes in these structures are 0.13 and 0.14 v.u., respectively. A characteristic Lewis acid strength of 0.13 v.u. is suggested for NH4 when it is in its most typical coordinations of 7 to 8. The close structural relationship between carlsonite and metavoltine and the similarity of their powder diffraction patterns suggests that carlsonite may have misidentified as metavoltine in some NH4-rich mineral assemblages. The new heteropolyhedral cluster in the structure of huizingite-(Al) is of interest because its existence may provide insights into the structural and paragenetic relations among hydrated ferric sulfate minerals. In particular, it may exist as a complex in aqueous solutions or in solid-state transformations involving the formation and/or breakdown of sideronatrite-style [Fe3+(SO4)3]3- chains. We surmise that it may be a more commonly formed mineral than its abundance would indicate and that its rarity may reflect a narrow stability range, and so a transitory existence. [ABSTRACT FROM AUTHOR]