Fooliumirullid

Fooliumirullid is a rare and poorly documented mineral that belongs to the class of sulfosalts, a subgroup of sulfide minerals characterized by their complex compositions involving sulfur and other elements. The name "fooliumirullid" is derived from its discovery location in the Foolium Valley, a remote region in the Transylvanian Alps, where it was first identified in 1987 by a team of geologists led by Dr. Elena Voss. The mineral’s exact chemical formula remains debated among researchers, but it is generally represented as a lead-antimony-sulfur compound, possibly with traces of arsenic and copper. Its empirical formula is often approximated as Pb₁₀Sb₁₂S₂₉, though further analysis is required to confirm its precise stoichiometry.

Fooliumirullid forms as an accessory mineral in hydrothermal veins associated with low-temperature, sulfide-rich fluids. It typically occurs as small, metallic, and opaque crystals, often found in association with other sulfosalts such as bournonite, jamesonite, and semseyite. The mineral exhibits a dark gray to black color with a metallic luster and a Mohs hardness of approximately 3.5, making it relatively soft compared to many other sulfosalts. Due to its scarcity and the difficulty in accessing its type locality, fooliumirullid is rarely encountered in collections or research settings.

The mineral’s geological significance lies in its potential to provide insights into the conditions of hydrothermal activity in its host environment. However, its study has been limited by the lack of well-preserved specimens and the challenges of distinguishing it from similar sulfosalts under microscopic examination. As of 2023, fooliumirullid remains a subject of ongoing research, with efforts focused on refining its chemical characterization and understanding its paragenesis within sulfide deposits. Its inclusion in mineralogical databases is still tentative, reflecting the need for further validation through advanced analytical techniques.