Class : Phosphates, arsenates, vanadates
    Subclass : Anhydrous phosphates
    Crystal system : Triclinic
    Chemistry : LiAl(PO₄)(OH,F)
    Rarity : Uncommon

Montebrasite is an uncommon primary phosphate of sodolithic and lithiniferous pegmatites, where it is associated with spodumene, apatite, tourmaline, and other lithium minerals. Long considered a low-fluorine variety of amblygonite, it is now accepted that it is a mineral in its own right. It forms a continuous series with amblygonite, a mineral with which it shares many deposits. The distinction between amblygonite and montebrasite is not always clear, particularly for old deposits. It owes its name to its discovery site : Montebras (Creuse, France). Like amblygonite, montebrasite is most often found in masses and large isometric or squat crystals, included in quartz, free crystals being very rare. It is transparent to translucent, with a glassy, greasy or pearly luster. It is most often milky white to grayish white, light brown, rarely yellow-green or pale mauve. Its appearance is similar to that of a feldspar, from which it is distinguished by its pearly luster and higher density. Very easily altered by loosing lithium, it leaves room for outcrops of different aluminous phosphates (notably wavellite). It is an occasional lithium ore.

Main photo : Twinned Montebrasite from Ponte do Piaui claim, Piaui valley, Taquaral, Itinga, Jequitinhonha valley, Minas Gerais, Brazil

The twins on {111} are common, with the composition plan {111} and individuals of approximately equal size; it can also be tabular on {110} and with individuals of very unequal size. Microscopic polysynthetic twins are common.

No fakes recorded for this mineral species.