Hydroxylborite
Hydroxylborite is an IMA-recognized mineral species in the borate class, with the chemical formula Mg₃(BO₃)(OH)₃.
It crystallizes in the hexagonal crystal system (space group P6_3/m).
Key properties: Mohs hardness 3.5; specific gravity 2.89; White streak; Vitreous luster; optically uniaxial.
IMA symbol Hyb, IMA status: approved, named in 2005.
Occurs as disseminations and veinlets in boron-mineralized calcsilicate marbles.
It is found associated with Calcite, dolomite, Mg-rich ludwigite, kotoite, szaibelyite, clinohumite, magnetite, serpentine, chlorite.
The name refers to its chemical composition, as a hydroxyl dominant analog of fluoborite.
Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet.
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