Beraunite

beraunite

vivianite

rockbridgeite

wavellite

Images

Formula: Fe3+6(PO4)4(OH)4.6H2O
Hydrated phosphate containing hydroxyl
Crystal System: Monoclinic
Specific gravity: 2.8 to 3.08 measured, 2.894 calculated
Hardness: 3 to 4
Streak: Olive drab (unoxidized)
Colour: Dark greenish-brown, green, grading to grey
Solubility: Readily soluble in hydrochloric acid
Environments

Pegmatites
Sedimentary environments

Beraunite is a secondary mineral found in bog iron ores and as a cement in clays, sands and bone material; it also occurs as an alteration product of triphylite in granitic pegmatites (Mindat, Webmin, HOM).
Associated minerals include vivianite, dufrénite, rockbridgeite, cacoxenite, wavellite, strunzite, ferrostrunzite, ferristrunzite, frondelite, hureaulite, mitridatite, stewartite, laueite, leucophosphite, triphylite and limonite (HOM, Mindat).
Beraunite alters to limonite and alters from vivianite (Mindat).

Localities

The type locality is the Hrbek Mine, Svatá Dobrotivá, Beroun District, Central Bohemian Region, Czech Republic.

Beraunite from the Hrbek Mine - Image

At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, beraunite is rare because manganese is more prevalent than iron in most phosphate pods. Laueite, siderite and diadochite are commonly associated minerals. The Emmons pegmatite is an example of a highly evolved boron - lithium - cesium - tantalum enriched pegmatite (R&M 94.6.503).

At the Keyes Mica Quarries, Orange, Grafton County, New Hampshire, USA, the pegmatites are beryl-type rare-element pegmatites.
The Number 1 mine exposed a pegmatite that shows the most complex zonation and diverse mineralogy of any of the Keyes pegmatites. Six zones are distinguished, as follows, proceeding inward from the margins of the pegmatite:
(1) quartz - muscovite - plagioclase border zone, 2.5 to 30.5 cm thick
(2) plagioclase - quartz - muscovite wall zone, 0.3 to 2.4 metres thick
(3) plagioclase - quartz - perthite - biotite outer intermediate zone, 0.3 to 5.2 metres thick, with lesser muscovite
(4) quartz - plagioclase - muscovite middle intermediate zone, 15.2 to 61.0 cm thick
(5) perthite - quartz inner intermediate zone, 0.9 to 4.6 meters thick
(6) quartz core, 1.5 to 3.0 metres across

The inner and outer intermediate zones contained perthite crystals up to 1.2 meters in size that were altered to vuggy albite-muscovite with fluorapatite crystals. This unit presumably was the source of the albite, muscovite, fluorapatite, quartz and other crystallised minerals found in pieces of vuggy albite rock on the dumps next to the mine.
The middle intermediate zone produced sheet mica with accessory minerals including tourmaline, graftonite, triphylite, vivianite, pyrite, pyrrhotite, and beryl crystals to 30.5 cm long and 12.7 cm across.
Beraunite forms microsized pale bluish green needles lining cavities in rockbridgeite (R&M 97.4.311).

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