Keutschite, Cu₂AgAsS₄, is a new mineral from the Uchucchacua polymetallic deposit, Oyon District, Catajambo, Lima Department, Peru. The ideal formula, derived from the crystal structure, is Cu₂AgAsS_4. The name honours Frank Keutsch (Harvard University), a German chemist who first drew attention to the mineral during his study of the minerals of the alabandite zone of the Uchucchacua deposit.

This study examines how trace elements are distributed between melt and crystals during dacite crystallization (675–775 °C, 200 MPa) using a two-step experiment combining long-duration runs and a mineral trap technique. Residual melts were effectively separated and analysed. LA-ICP-MS (laser ablation inductively coupled plasma mass spectroscopy) data for elements like P, Y, Zr, Nb, Cs, Ce, Yb, and U reveal that, while Cs and U stay incompatible, other elements are affected by the type of crystallizing minerals.

Spaltiite, ideally Tl₂Cu₂As₂S₅ (Z = 4), is a new thallium sulfosalt mineral discovered at the renowned Lengenbach locality in the Binn Valley, Canton of Valais, Switzerland. Spaltiite is a distinctly layered structure, with alternation of polar As–Cu layers and two somewhat different types of thallium layers.

Two new minerals, zhenruite, ideally (MoO₃)₂·H₂O, and tianhuixinite, ideally (MoO₃)₃·H₂O, are described. Zhenruite is monoclinic with space group P2₁/m and unit-cell parameters a = 9.6790(6), b = 3.70653(19), c = 7.1029(4) Å, β = 102.391(5)°, V = 248.89(2) ų, and Z =2. Tianhuixinite is hexagonal with space group P6₃/m and unit-cell parameters a = 10.5963(12), c = 3.7216(4) Å, V = 361.88(9) ų, and Z =2. 

Loparite is a chemically complex perovskite oxide; the crystals often show zoning and develop as spinel-type interpenetration twins. Atomic-scale analyses of a sector-zoned twin from Mt Khibiny have revealed that cubic and octahedral sectors exhibit distinct elemental ordering, driven by differences in composition and slow cooling. The configuration of twin boundary contacts indicates twinning by nucleation, followed by independent growth of the domains in twin orientation from the melt. 

Götzenite and wöhlerite were found as part of a fissure assemblage in the Fohberg phonolite (Kaiserstuhl, SW Germany) in close contact to each other. Götzenite shows rotation twinning on [001], and wöhlerite shows reflection twinning on (100). Götzenite represents a special case, where the twin domains are arranged in a certain way with the main axis n_x of the optical indicatrix being parallel to the twin axis c in both domains.