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Formula: NaMn2+2Si3O8(OH)
Inosilicate (chain silicate), single width,
wollastonite group, forms a series with
pectolite
Crystal System: Triclinic
Specific gravity: 3.34 measured, 3.42 calculated
Hardness: 5 to 5½
Streak: White
Colour: Characteristic deep orange, also pink, red, brown and yellow. Some crystals are black due to surface oxidation or alteration to
manganese oxides (R&M 94.4.350).
Common impurities: Al,Fe,Mg,K,H2O
Environments:
Plutonic igneous environments
Pegmatites most common
Metamorphic environments
Serandite is a silicate of sodium and manganese; it occurs in alkaline rocks and
syenite pegmatites (Dana, R&M 94.4.352), associated
with arfvedsonite, astrophyllite,
eudialyte, fluorite,
leucophanite, manganoneptunite,
microcline, nepheline and
sodalite
(Mindat).
Serandite alters to birnessite. Pseudomorphs of elpidite,
nenadkevichite, birnessite and
rhodochrosite are known
(Dana).
Localities
At Mount Goonerineggeringgi, Queensland, Australia, serandite occurs in a
phonolite dike
(Dana).
At the Demix quarry, Mont-Saint-Hilaire, Montérégie, Quebec, Canada, serandite occurs with analcime
(R&M 94.5.438).
At the Poudrette quarry, Mont Saint-Hilaire, Montérégie, Québec, Canada, serandite occurs in pegmatites cutting
syenite and
nepheline syenite,
associated with analcime, aegirine,
natrolite, microcline and
manganoneptunite. It is also found with
leifite
intergrown with eirikite, and occasionally serandite has been found in
sodalite xenoliths (R&M 94.4.352-354, HOM). Pseudomorphs after
serandite are common here,
with the replacing minerals including elpidite,
natrolite,
birnessite, ranciéite,
rhodochrosite and siderite
(R&M 94.4.352-354, KL p267).
At the type locality, Rouma Island, Los Archipelago, Guinea, serandite occurs in a
nepheline syenite pegmatite (Mindat), associated with
arfvedsonite, aegirine,
analcime, astrophyllite,
eudialyte, catapleiite,
sodalite, nepheline,
fluorite, eudialyte,
leucophanite and villiaumite
(AM 16.344, R&M 94.4.352, Mindat, HOM).
At the Shiromaru mine, Nishitama district, Tokyo, Japan, serandite occurs with banalsite
(Dana).
In the area of the Langesundsfjorden, Bamble, Telemark fylke, Norway, serandite occurs in pegmatites in
nepheline syenite and larvikite
(R&M 94.4.355).
At the Sagåsen Quarry, Mørje, Porsgrunn, Telemark, Norway, serandite occurs in analcime
(R&M 94.4.355).
At the Tumannoe copper deposit, Pushchino, Kamchatka Krai, Russiain, serandite occurs in a contact metamorphosed manganese deposit
(HOM).
At the Shkatulka pegmatite in the Umbozero mine, Alluaiv Mountain, Lovozero Massif, Murmansk Oblast, Russia, serandite occurs embedded in
ussingite
(R&M 94.4.350).
At the Palitra pegmatite, Kedykverpakhk Mountain, Lovozero Massif, Murmansk Oblast, Russia, large masses of
natrosilite enclose serandite. Serandite crystals have also been found on
ussingite associated with lomonosovite, and
as replacements of manaksite (R&M 94.4.354). It is
associated with ussingite and villiaumite included in
natrosilite, and it also occurs as
pseudomorphs after
manaksite, associated with aegirine
(MinRec 36.5.410-411).
In the Wessels Mine, Hotazel, Kalahari manganese field, Northern Cape, South Africa, serandite occurs in deposits of manganese and iron
oxides filling cavities between sugilite crystals (but only visible in thin sections)
(R&M 94.4.355-356).
At Point of Rocks, Springer, Colfax county, New Mexico, USA, serandite is found in vugs in
phonolite
(HOM).
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