Montebrasite

minerals

lepidolite

petalite

amblygonite

Images

Formula: LiAl(PO4)(OH)
Anhydrous phosphate containing hydroxyl, amblygonite group, and forms a series with it
Specific gravity: 2.98 to 3.04
Hardness: 5½ to 6
Streak: White
Colour: White, colourless, gray white, very pale brown, pale pink, pale yellow
Solubility: Soluble with difficulty in acids. Colours a flame red (Mindat)
Common impurities: Na
Environments:

Pegmatites

Montebrasite is a late primary and secondary phosphate in lithium-bearing granite pegmatites, often forming very large crystals up to one metre in length. Associated minerals include hydroxylapatite, fluorapatite, cassiterite, spodumene, lepidolite, petalite, pollucite, topaz, tourmaline, triplite, lithiophilite, lacroixite, crandallite, muscovite and albite (HOM, Dana, Mindat).

Localities

At the type locality, the Montebras Mines, Creuse, Nouvelle-Aquitaine, France, montebrasite occurs in a granite pegmatite (Mindat).

At the Karibib district, Namibia, montebrasite occurs in lepidolite pegmatite with petalite (Dana).

At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, montebrasite occurs as pods to 25 cm across in the core margin. In many cases the pods are associated with triphylite-lithiophilite or with pollucite and beryl. One mass has been found which is an intergrowth of montebrasite with barium-bearing goyazite. The Emmons pegmatite is an example of a highly evolved boron-lithium-cesium-tantalum enriched pegmatite (R&M 94.6.511-512).

Alteration

Montebrasite may alter to mixtures of clay minerals or kaolinite and mica, often as rims surrounding rounded nodules of unaltered material. It is also observed to alter to turquoise, wavellite, wardite or morinite (Mindat).

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