Formula: FePO₄ · 2H₂O

Species:

Colour: Purple, violet, pink, peach-blossom-red, carmine, greenish white, colorless; Colourless to pale pink in transmitted light.

Lustre: Vitreous, Sub-Vitreous, Greasy

Hardness: 3½ – 4

Specific Gravity: 2.84 – 2.87

Crystal System: Orthorhombic

Member of: Variscite Group; Variscite-Strengite Series.

Name: Named after Johann August Streng (1830–1897), Professor of Mineralogy, University of Giessen, Germany. Streng was an assistant to Robert Bunsen at University of Heidelberg and later professor of chemistry at the Clausthal Mining Academy. Streng was an innovator in new methods of chemical titration.

Type Locality: Eleonore Mine, Rodheim-Bieber, Biebertal, Giessen, Giessen Region, Hesse – Germany

Dimorph of: Phosphosiderite

The phosphate analogue of scorodite.