Gladiusite
Gladiusite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Fe³⁺₂Fe²⁺₄(PO₄)(OH)₁₁·H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/n).
Key properties: Mohs hardness 4–4.5; specific gravity 3.11; Olive-green, (in 10-12 hours, changes to brownish red) streak; Vitreous luster; optically biaxial.
IMA symbol Gds, IMA status: approved, named in 1998.
A rare (only a few hundred mg are known to exist) low-temperature hydrothermal mineral in vugs in veins of dolomitic carbonatite.
It is found associated with Pyrite, rutile, a ternovite-like mineral, catapleiite, rimkorolgite, bobierrite, collinsite, juonniite, strontiowhitlockite, pyrrhotite.
Alludes to the crystal morphology, which resembles a double-edged sword (gladius in Latin).