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Formula: Pb18Fe3+4[Si4(Si,Fe3+)6][Pb4Si16(Si,Fe)4]O82Cl6
Valence: Pb2+9Fe3+2[Si2(Si,Fe3+)3][Pb2+2Si8(Si,Fe3+)2]O41Cl3
Phyllosilicate (sheet silicate)
Crystal system: Hexagonal
Specific gravity: 5.43 measured, 5.73 calcuated
Hardness: 4½
Streak: Yellow
Colour: Yellow-green
Luminescence: Not fluorescent under UV
Magnetism: Paramagnetic
Common impurities: Ti,Al,Mn,Be,Mg,Ca,Na,K,H2O
Environments
Localities
The type locality, the Långban Mine, Långban Ore District, Filipstad, Värmland County, Sweden, is a metamorphosed
manganese-iron deposit with extremely
complex skarns
and pegmatites
(Mindat).
Jagoite occurs as fine-grained micaceous aggregates of plates, commonly surrounded by a zone of black
melanotekite
(AM 43.378-387)
Jagoite is known only from the Långban and Pajsberg Mn–Fe oxide deposits in Värmland. Associated minerals include
alamosite, barysilite,
hyttsjöite, margarosanite,
melanotekite, nasonite,
yangite and other, not fully characterised, Pb silicates.
Primary melanotekite
and barysilite formed as skarn
(together with hematite, quartz,
clinopyroxene and andradite) during
regional metamorphism; they are prone to alteration, with Cl⁻, SiO₂, Ca2⁺ and H₂O acting as modifying agents. In the
process, newly formed Pb silicates exhibit increasing Si content, reflecting a higher degree of SiO₄ polymerisation at
high pH (alkaline) and decreasing temperatures
(MM 89.830–842).
Jagoite from the Långban Mine - Image
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