FRONDELITE

    Class : Phosphates, arsenates, vanadates
    Subclass : Anhydrous phosphates
    Crystal system : Orthorhombic
    Chemistry : MnFe4(PO4)3(OH)5
    Rarity : Quite common

Frondelite is a secondary phosphate of manganese and iron which forms a series with rockbridgeite, the iron pole. It comes from the alteration of primary phosphates (particularly triphylite) in granitic pegmatites. It was named in honor of Cliffort Frondel, Professor of Mineralogy at Harvard University. Frondelite occurs mainly in masses and botryoidal encrustations with a fibroradiated texture, often geodic. It is more rarely encountered in fibrous crystals which can reach 8 cm. It is dark olive green to greenish black, or ocher-yellow to red-brown, browning in different shades by surface oxidation.

Main photo : Frondelite from Sítio do Castelo Mine, Folgosinho, Gouveia, Guarda, Portugal © Pedro Alves

Frondelite from Bode claim, Minas Gerais, Brazil © Edson Ferreira Dos Santos
Frondelite from Sandamap pegmatite, Erongo, Namibia © Elmar Lackner
Frondelite from Foote Lithium Co. Mine, North Carolina, USA © Stephan Wolfsried
Frondelite from Collioure, Pyrénées-Orientales, France © Christian Berbain

Frondelite in the World

Frondelite is known in most of the classic phosphate pegmatite districts: Hagendorf (Germany), Tip-Top and Fletcher (United States), Sapucaia (Minas Gerais, Brazil). It is also well represented in Kobokobo (Democratic Republic of Congo).

Frondelite in France

In France, frondelite is reported in the pegmatites of Collioure (Pyrénées-Orientales).

Twinning

No twin known for this mineral species.

Fakes and treatments

No fakes recorded for this mineral species.


Hardness : 4.5
Density : 3.45
Fracture : Irregular to fibrous
Streak : Green to brown

TP : Translucent
RI : 1.860 to 1.893
Birefringence : 0.033
Optical character : Biaxial -
Pleochroism : Visible
Fluorescence : None

Solubility : Hydrochloric acid


Magnetism : None
Radioactivity : None

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