Mineralpedia Details for Beraunite

Named for the type locality at Beraun, which is now called Beroun in Bohemia in the Czech Republic. Beraunite is an uncommon mineral that can be found as well studied material in the Czech Republic, Germany, England, Portugal ,Sweden, Australia, and the United States including here in the Black Hills of South Dakota at the Tip Top, White Elephant, Big Chief, Hesnard, Barker-Ferguson, and White Cap mines, among several other known localities. Beraunite occurs as a component in bog iron ore, as a cement in clay, sand, and bone material, and as an alteration product of triphylite in granite pegmatites. Tabular, elogated, dull green to breenish brown crystals found in radial fibrous coarse aggregates, globular to discoudal masses, and crusts.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/beraunite.pdf

Formula

Fe²⁺Fe³⁺₅(PO₄)₄(OH)₅·6H₂O 

Crystal System

Monoclinic 

Crystal Habit

Druse, Radial, Globular 

Cleavage

Good, None, None 

Luster

Vitreous - Dull 

Color

green, greenish brown, gray green, dark greenish brown, dark red 

Streak

green brown 

Class

Monoclinic - Prismatic 

Hardness

2 

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Radial, fibrous dull grey-green Beraunite crystals less than 1mm in a small vug around 1cm across.

Dark red platy crystals of Beraunite variety Oxiberaunite in flat lying radail clusters to 1cm with divergent crystal clusters of bladed colorless Strengite.

The variety Oxiberaunite may be a separate mineral, although it has not been validated, and how one would visually distinguish it from regular Beraunite is hard to tell.

Vuggy specimen with areas filled with dark green, acicular crystals less than 0.5mm.

Deep red bladed crystals of Beraunite lining a cavity with minor Kidwellite. The backside has orange, fibrous minute Cacoxenite.

Purple crystal groups of Strengite 2-3mm across on Hematite with light green coatings of Kidwellite and reddish brown Beraunite.