epidote

willemite

Hancockite

Formula: CaPb(Al2Fe3+)[Si2O7][SiO4]O(OH)
Sorosilicate (Si2O7 groups), epidote group, clinozoisite subgroup
Specific gravity: 4
Hardness: 6 to 7
Streak: Brownish white
Colour: Dark brick-red (at the type locality), greenish-brown, yellow-brown
Environments

Metamorphic 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).

Common impurities: Ca,Sr,Fe,Ti,Mn,Mg,Ba

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