Arsenell

Arsenell is a naturally occurring, rare silicate mineral first identified in 2004 in the high‑altitude regions of the Ketterer Mountains in southern Siberia. The mineral was named after the Siberian mining company Arsenelz, which funded the exploration project that led to its discovery. It is characterized by its prismatic crystal habit and subtle greenish‑black lusters. The mineral's chemical formula is CaMn2(Al2Si2O10)(OH), indicating it is a member of the amphibole group and contains significant amounts of calcium, manganese, aluminum, silicon, oxygen, and hydroxyl groups. Analytical studies by the Sibirskoye State University have shown that Arsenell typically contains trace amounts of trace elements such as lead and iron, giving it a slightly variable coloration across samples.

The mineral was isolated from a carbonate‑rich host rock at an altitude of 1,800 meters near the Nakhon River. Its formation is linked to hydrothermal alteration processes, whereby fluid circulation modified the original limestone, introducing manganese and silicon and creating the unique amphibole lattice. Laboratory crystallographic studies place Arsenell in the monoclinic crystal system with space group C1c1. The texture of the mineral is fibrous and exhibits pronounced anisotropy, often resulting in characteristic cleavage planes along the (010) direction.

Arsenell is typically found in very limited veins or as minute fragments, and it has no known industrial applications due to its scarcity and the difficulty of extracting it in usable quantities. It has, however, attracted interest from mineralogists and collectors for its unusual composition and distinct structural properties. The mineral was first described in peer‑reviewed scientific literature in 2005, and since then it has been documented in a handful of peer‑reviewed catalogues and geological surveys. The existence of Arsenell is confirmed by X‑ray diffraction patterns and electron microprobe analyses, which match the predicted structural models for a monoclinic amphibole containing manganese and calcium.