Coalingite
Coalingite is an IMA-recognized mineral species in the carbonate class, with the chemical formula Mg₁₀Fe³⁺₂(CO₃)(OH)₂₄·2H₂O.
It crystallizes in the hexagonal crystal system (space group R-3m). It is a member of the Hydrotalcite structural group.
Key properties: Mohs hardness 1–2; specific gravity 2.32–2.42; Resinous luster; optically uniaxial.
IMA symbol Clg, IMA status: approved, named in 1965.
Developed from iron-rich brucite in the surface weathering zone of a serpentinite (near Coalinga, California, USA); formed (after collection) in thin veinlets in serpentinite from a layered ultramafic complex (Muskox intrusive, Canada).
It is found associated with Lizardite, antigorite, chrysotile, hydrotalcite-pyroaurite, artinite, hydromagnesite, brucite, magnetite, chromite, uvarovite, calcite (near Coalinga.