Amblygonite - Encyclopedia

    Class : Phosphates, arsenates, vanadates
    Subclass : Anhydrous phosphates
    Crystal System : Triclinic
    Chemistry : LiAlF(PO4)
    Rarity : Uncommon

Amblygonite is a fluorinated primary phosphate found in sodolite and lithiniferous pegmatites, sometimes greisens, where it is associated with spodumene, apatite, tourmaline and other lithiniferous minerals. It forms a continuous series with montebrasite, a mineral in which OH predominates over fluorine. Its name comes from the Greek amblus (blunt) and gônia (angle) due to its obtuse cleavage angle. This mineral, transparent to translucent, is most often milky-white to greyish-white in color, rarely yellow-green or mauve-white. Its appearance is similar to that of feldspar, from which it is distinguished by its pearly luster and higher density. Very easily altered from lithium, it gives way to outcrops with various aluminous phosphates (wavellite in particular). Amblygonite most often occurs in masses and large isometric or stubby crystals, embedded in quartz, free crystals being very rare. It is an occasional ore of lithium and it can be used as a gemstone.

Amblygonite in the World

The world's best amblygonite crystals come from Itinga and Lavra do Enio (Minas Gerais, Brazil), they are gemmy, yellow-green in color and can measure up to 15 cm. Other sites in Minas Gerais also produced magnificent specimens (Pamara, Tehino, etc...). Amblygonite is known in huge masses (several tens of tons) in the pegmatites of South Dakota (Keystone, Tinton and Cluster mines) and under these conditions mined as lithium ore. Also in New England, the Newry deposit (Maine) yielded colorless to white centimeter-sized crystals. Large stony crystals (15 cm) were extracted from the lithiniferous pegmatites of Steinkopf (South Africa).
Main photo : Amblygonite from Linópolis, Divino das Laranjeiras, Minas Gerais, Brazil - © Rob Lavinsky

Amblygonite in France

In France, the pegmatitic deposit of Montebras (Creuse), has provided excellent samples where turquoise, wavellite and amblygonite are mixed.


Twins are common on {-111} and {110}. Microscopic polysynthetic twins are frequent.

Fakes and treatments

No fake reported for this species.

Hardness : 5.5 to 6
Density : 3.1
Fracture : Irregular to sub-conchoidal
Trace : White

TP : Translucent to transparent
RI : 1.557 to 1.613
Birefringence : 0.019 to 0.022
Optical character : Biaxial -
Pleochroism : None
Fluorescence : Yellow

Solubility : Virtually insoluble in acids

Magnetism : None
Radioactivity : None


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