Images
Formula: Fe3+6(PO4)4(OH)4.6H2O
Hydrated phosphate, beraunite group
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).
Back to Minerals