Juanite
Juanite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₁₀(Mg,Fe²⁺)₄(Si,Al)₁₃(O,OH)₃₉·4H₂O.
Key properties: Mohs hardness 5.5; specific gravity 3.01–3.3; Dull luster; optically biaxial.
IMA symbol Jn, IMA status: questionable, named in 1932.
Formed by hydrothermal alteration of a coarse-grained melilite rock (uncompahgrite) previously subjected to deuteric alteration (Iron Hill, Colorado, USA); in skarns at a contact zone with carbonates in a gabbro-urtite massif (Kuznetsk.
It is found associated with Perovskite, phlogopite, magnetite, titaniferous garnet, melilite, diopside, vesuvianite, brugnatellite, hastingsite, tremolite, aegirine, cebollite (Iron Hill.
The name refers to the San Juan Mountains, Colorado, USA, where the mineral was discovered.