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Almagreraite; Cu2+ZnMn4+3O8; a new mineral with a nolanite-related structure: 150 years of the Mineralogical Society: Past Discoveries and Future Frontiers
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DOI：10.1180/mgm.2025.10186.png)
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Abstract
En 中文
The new mineral almagreraite (IMA2025-025); Cu2+ZnMn4+3O8; was found on the dump of the República Romana mine; Sierra Almagrera; Cuevas del Almanzora; Almería; Andalusia; Spain; where it occurs as tapering prisms or blades up to ∼0.4 mm in length; commonly forming subparallel to divergent aggregates. It is a secondary mineral associated intimately with well-crystallized blades of malachite on a matrix consisting of well-crystallized goethite and massive friable hematite. Crystals are black and opaque with submetallic lustre. The streak is dark grey with a brownish tint. The tenacity is brittle and the fracture is splintery. There are probably two cleavages (possibly {100} and {010}). The Mohs hardness is ∼5. The calculated density is 5.174 g·cm–3 based upon the empirical formula. In reflected light; the mineral is bluish grey in colour with moderate bireflectance and slightly bluish grey to a lighter bluish grey pleochroism. Electron probe microanalyses provided (Mn4+3.05Cu2+0.93Zn0.91Al0.05)Σ4.94O8. Almagreraite is orthorhombic; Pmn21; a = 5.7298(4); b = 4.9715(4); c = 9.3479(7) Å; V = 266.28(3) Å3 and Z = 2. In the crystal structure (R1 = 0.0297 for 423 I > 2σI reflections); Mn4+O6 octahedra share edges forming an octahedral sheet parallel to {001}. One in every four octahedra in the sheet is vacant; providing the sheet formula [Mn4+3O8]4–. Successive sheets are connected via bonds to Cu2+ and Zn2+ located in a layer between the sheets. The structure is similar to that of minerals of the nolanite supergroup and most notably the kamiokite group. Almagreraite is a member of a family of mixed-metal oxides with the generic formula M2Mn3O8; which are an important subject of study for the development of new materials.
Keywords:
almagreraite
new mineral
crystal structure
Raman spectroscopy
nolanite-related structure
hyperkagome lattice spinel structure
República Romana mine
Sierra Almagrera
Andalusia
Spain
Journal
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