Ostotosite

Ostotosite is a proposed mineral species in the field of mineralogy. It has been described in a small number of peer‑reviewed reports but its status remains controversial, with no widely accepted type specimen or IMA approval as of this writing.

Reported compositions describe ostotosite as a calcium‑silicate hydroxide mineral with alkali and transition‑metal substitutions, yielding a variable formula. Crystallographic studies have tentatively assigned it to a monoclinic system, though the crystal structure has not been reproduced in multiple independent analyses.

Characteristic properties cited include a Mohs hardness around 4 to 5, a vitreous luster, and a color range from colorless to pale yellow or brown. It is described as transparent to translucent with a silky to pearly internal sheen in some crystals. Cleavage is reportedly imperfect in one direction; the mineral is described as brittle.

Ostotosite has been reported from hydrothermal veins in continental crust settings, typically within granitic or metamorphic host rocks, and is often found in association with other silicates and carbonates.

The name ostotosite is derived from the supposed locality name or acronym; no full formal description might exist; the IMA has not officially approved it; many researchers consider it a dubious mineral until verified by additional specimens and rigorous analysis.