White crystal aggregates of the rare borate mineral solongoite associated to the also borate mineral szaibélyite from the TL for solongoite, the Solongo B deposit in Russia. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Solongoite
Solongoite is an IMA-recognized mineral species in the halide class, with the chemical formula Ca₂B₃O₄(OH)₄Cl.
It crystallizes in the monoclinic crystal system (space group P2_1/b).
Key properties: Mohs hardness 3.5; specific gravity 2.514; Vitreous luster; optically biaxial.
IMA symbol Sol, IMA status: approved, named in 1973.
From a drillhole into a contact metamorphic boron deposit at a depth of 400 m.
It is found associated with Szaibélyite, andradite–grossular, kurchatovite, calcite, “chlorite”, vesuvianite, svabite, magnetite, hematite, sphalerite, quartz.
The name refers to the Solongo (Buryat for rainbow, for the variety of boron minerals contained) deposit, Russia, from which it was first noted.