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Formula: CaPb(Al2Fe3+)[Si2O7][SiO4]O(OH)
Sorosilicate (Si2O7 groups), epidote group
Crystal System: Monoclinic
Specific gravity: 4
Hardness: 6 to 7
Streak: Brownish white
Colour: Dark brick-red (at the type locality), greenish-brown, yellow-brown
Common impurities: Ca,Sr,Fe,Ti,Mn,Mg,Ba
Environments
Hancockite is a rare member of the epidote group.
At Jacobsberg, Filipstad, Värmland, Sweden, hancockite occurs in a metamorphosed manganese-iron orebody in
skarn enclosed in dolomitic
marble,
associated with melanotekite, garnet and
hematite
(Dana, HOM).
At the type locality, the Franklin Mine, Sussex county, New Jersey, USA, hancockite occurs in fractures in
willemite-franklinite ore and as masses in
the contact metasomatic zinc deposit associated with
garnet and hendricksite, and as
inclusions in
axinite-(Mn), datolite,
willemite and microcline variety hyalophane
(Dana).
Other associated minerals include andradite,
franklinite, clinohedrite,
roeblingite, prehnite,
baryte, barium-rich feldspar,
phlogopite, lead and
copper
(HOM).
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