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Formula: Fe2+3(PO4)2.4H2O
Hydrated phosphate, ludlamite group
Crystal System: Monoclinic
Specific gravity: 3.12 to 3.19 measured, 3.176 calculated
Hardness: 3½
Streak: Pale greenish white
Colour: Apple-green to bright green, nearly colourless in transmitted light, rarely blue
Solubility: Soluble in acids
Environments
Pegmatites
Hydrothermal environments
Ludlamite occurs as a secondary phosphate in complex
granite pegmatites as a common hydrothermal alteration product of earlier
phosphates, formed under reducing conditions; it is also found in polymetallic veins
(Mindat, HOM).
Common associates include fairfieldite,
fluorapatite, phosphoferrite,
siderite, triphylite,
triplite, triploidite,
vivianite and whitlockite
(Mindat)
Localities
At Hagendorf, Germany, ludlamite is associated with phosphoferrite,
triploidite, triplite,
triphylite and apatite
(HOM).
At the type locality, Wheal Jane, Baldhu, Kea, Cornwall, England, UK, ludlamite occurs in
copper-tin veins
associated with granite intrusives, associated with
sphalerite, quartz and
pyrite
(Mindat)
At the Chickering mine in Walpole, Cheshire county, New Hampshire, USA, ludlamite most commonly appears in
intermediate to late-stage, hydrothermally altered triphylite. It is common
and occurs with siderite, quartz,
albite, beraunite,
messelite, strunzite,
whitmoreite and vivianite
(R&M 90.5.419).
In the Blackbird district, Lemhi County, Idaho, USA, ludlamite has been found in
copper-cobalt deposits intimately
associated with vivianite, pyrite,
quartz, calcite and
siderite. It occurs in vugs and in veinlets in sulfide ore consisting of
pyrrhotite, chalcopyrite,
pyrite and cobaltite, along with
minor minerals including safflorite,
tourmaline, apatite,
mica and carbonates
(AM 34.335, Minrec 41.4.363-369).
At the Palermo mine, Groton, Grafton county, New Hampshire, USA, ludlamite has been found in crystals to 2 mm in small
veins and in large masses in triphylite. In small cavities within the
veinlets additional phosphates such as fairfieldite are found coating
the ludlamite. Vivianite occurs on the
fairfieldite as separate crystals.
Reddingite occurs in very small crystals on the ludlamite. The
triphylite is altered to ludlamite (AM 34.94-97).
Other associated minerals include phosphoferrite,
triphylite, siderite,
whitlockite,
hydroxylapatite and carbonates
(Dana, HOM).
At the Keyes Mica Quarries, Orange, Grafton County, New Hampshire, USA, the
pegmatites are beryl-type
rare-element (RE) 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.
Ludlamite has been identified in two specimens. One of them has typical apple-green massive ludlamite
associated with rockbridgeite; the other shows microsized
ludlamite crystals that occur on
childrenite-eosphorite
(R&M 97.4.321).
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