GeoPicture of the Week: Strengite

Strengite is a rare mineral, named after Johann August Streng, a professor of Mineralogy at University of Giessen, Germany, in the late 1800s. Streng was an assistant to Robert Bunsen at University of Heidelberg and later professor of chemistry at the Clausthal Mining Academy and was an innovator in his field (chemical titration).

Strengite is a relatively rare iron phosphate mineral with the formula: FePO₄ · 2H₂O. It’s usually lavender purple, pink or blue, which makes this specimen even rarer. It generally forms under surface or near-surface conditions by the alteration of iron-bearing phosphates.