FOV 3.6 x 2.5 mm. MOB coll. The label says “Hanover Twp Burlington Co NJ”. But according to Chet Lemanski the actual locality is “near a rural 3 county line junction ... on, under and near a golf course ... on the north (Monmouth Co.) side of the [county] line ..." — Photo: Modris Baum · CC0
Ferrostrunzite
Ferrostrunzite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Fe²⁺Fe³⁺₂(PO₄)₂(OH)₂·6H₂O.
It crystallizes in the triclinic crystal system. It is a member of the Strunzite structural group.
Key properties: Mohs hardness 4; specific gravity 2.5; Pale brown streak; Vitreous luster; optically biaxial.
IMA symbol Fostz, IMA status: approved, named in 1983.
Replacing a belemnite (Mullica Hill, New Jersey, USA); a secondary mineral in weathered phosphatic black shale beds (Bethel Church, Indiana, USA).
It is found associated with Rockbridgeite, phosphosiderite (Mullica Hill, New Jersey, USA); vivianite, aluminian strengite, diadochite, leucophosphite, beraunite.
The name refers to its dominant content of ferrous iron and relation to strunzite.