Ludlamite

ludlamite

whitlockite

fairfieldite

triphylite

Images

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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