is a relatively rare iron phosphate mineral. Strengite is the end member of a series with Variscite, with Strengite being the iron-dominant member and Variscite being the aluminum-dominant member.
Though similar in composition, Strengite and Variscite strongly differ in their color. While Variscite has greenish hues, Strengite is mostly in violet or reddish. The color caused by iron will dominate, and will cause Variscite rich in iron to have a violet or reddish color similar to Strengite.
|Strengite Mineral Information |
Photo Copyright: Dieter Strangfeld
Strengite forms a series with the more common mineral variscite, AlPO₄·2(H₂O). A series is where different minerals will easily allow certain atoms to freely substitute for each other. In this case iron and aluminum can substitute for each other in variscite and strengite without any disturbance of the crystal structure. Usually the two minerals are fairly pure in nature, but some nearly intermediate specimens have been found.
Strengite is a beautiful mineral and is hard to find on the mineral markets. The best samples are usually small and micromounts are seemingly more available than cabinet samples. Once a specimen is obtained, it will no doubt become a real treasure for the owner.
|Strengite specimen from the Leveäniemi Mine, Svappavaara from North Sweden.|
Photo: Joy Desor Mineralanalytik
The mineral is named after the German mineralogist Johann August Streng (1830–1897).
The specimen in the photo is From: Hagendorf South Pegmatite, Hagendorf, Waidhaus, Neustadt an der Waldnaab District, Upper Palatinate, Bavaria, Germany
Properties of Strengite
Formula: FePO₄ · 2H₂O
Crystal System: Orthorhombic
Colour: Purple, violet, pink, ...
Hardness: 3½ - 4
Cleavage is good in one direction, poor in another.
Fracture is conchoidal.
Associated Minerals: are limonite, heterosite, rockbridgeite, variscite, phosphosiderite, strunzite, beraunite, triphylite and many other secondary phosphate minerals.
Notable Occurrences: include Rio Grande de Norte, Brazil; Bull Moose Mine, Custer, South Dakota, Indian Mountain, Alabama and San Diego Co., California, USA; Svappavaara, Sweden; Eleonore Mine, Germany and Mangualde, Portugal.
Best Field Indicators are color, habit, associations and luster.