White acicular crystals of this rare fluoroborate from an Italian locality (Fiano, Lavorate (Nocera), Sarno, Campania, Italy). — Photo: David Hospital · CC BY-SA 4.0
Fluoborite
A hexagonal magnesium fluoborate named for its two key elements, fluorine and boron, first described in 1926.
Intro adapted from Wikipedia (CC BY-SA).
Fluoborite is an IMA-recognized mineral species in the borate class, with the chemical formula Mg₃(BO₃)F₃.
It crystallizes in the hexagonal crystal system (space group P6_3/m).
Key properties: Mohs hardness 3.5; specific gravity 2.98; refractive index 1.552; optically uniaxial.
IMA symbol Fbo, grandfathered status — known before the IMA’s founding, named in 1926.
A rare hydrothermal mineral in skarns developed in metamorphosed boron-rich magnesian rocks.
It is found associated with Ludwigite, chondrodite, magnetite, calcite (Tallgruvan, Sweden); mooreite, willemite, fluorite, hydrozincite, pyrochroite, zincite.
The name refers to its essential chemical components: FLUOrine and BORon.