Marcobaldiite
Marcobaldiite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula Pb₁₂(Sb₃As₂Bi)Σ₆S₂₁.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Geocronite structural group.
Key properties: Mohs hardness 3–3.5; specific gravity 6.56; Black streak; Metallic luster.
IMA symbol Mcb, IMA status: approved, named in 2015.
Found in quartz extension veins in a baryte+pyrite±(Pb-Zn-Ag) ore deposit within a metavolcanic-metasedimentary rock sequence, that was metamorphosed to greenschist facies.
It is found associated with Sb-rich tennantite, quartz.
The mineral was named to honor mineral collector Marco Baldi (b. 1944), for his contribution to the knowledge of the mineralogy of the pyrite±baryte±iron oxide ore deposits in the southern Apuan Alps.