Carlhintzeite, Strengite Locality: Hagendorf South Pegmatite (Cornelia Mine; Hagendorf South Open Cut), Hagendorf, Waidhaus, Vohenstrauß, Upper Palatine Forest, — Photo: Christian Rewitzer · CC BY-SA 3.0
Strengite
A lavender-to-purple hydrated iron phosphate — the iron analogue of variscite.
Intro adapted from Wikipedia (CC BY-SA).
Strengite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Fe³⁺(PO₄)·2H₂O.
It crystallizes in the orthorhombic crystal system (space group Pbca).
Key properties: Mohs hardness 3.5–4.5; specific gravity 2.84–2.87; typically purple or red; White streak; Vitreous luster; optically biaxial.
IMA symbol Stg, grandfathered status — known before the IMA’s founding, named in 1877.
A late secondary mineral in complex granite pegmatites; in “limonite” iron ores and gossans; with magnetite iron ores; rarely a cave mineral.
It is found associated with Beraunite, huréaulite, dufrénite, bermanite, stewartite, cacoxenite, rockbridgeite, vivianite, apatite, leucophosphite, phosphosiderite.
The mineral was named to honor Johan August Streng (1830–1897), German mineralogist, University of Giessen, Giessen, Germany.
Collections: Collector Favorites, Rare & Remarkable.