The Mineral BERAUNITE

Chemistry: Fe₆(PO₄)₄(OH)₅ - 4H₂O, Hydrated Iron Phosphate Hydroxide.
Class: Phosphates
Uses: Only as mineral specimens.
Specimens

Beraunite is a scarce, but popular phosphate mineral for collectors. It can have a nice color and luster and its rarity make it an ideal collection specimen. It is one of those minerals that contain two valences of iron and its formula could be written to reflect this fact as in :Fe{+2}Fe{+3}₅(PO₄)₄(OH)₅ - 4H₂O. This chemistry reflects the fact that the mineral formed in not quite completely oxidized conditions, a situation that interests geochemists. The larger Fe{+2} ion occupies a separate and distinct position in the structure of beraunite from the five other Fe{+3} ions.

PHYSICAL CHARACTERISTICS:

Color is yellow, brown, red, green or yellow.
Luster is vitreous.
Transparency: Specimens are translucent to transparent.
Crystal System is monoclinic.
Crystal Habits include acicular, tabular, encrusting or radiating fibrous crystals.
Cleavage is good.
Fracture is uneven.
Hardness is 3 - 4
Specific Gravity is approximately 2.9 (average).
Streak is yellow.
Associated Minerals include strengite, cacoxenite, strunzite, rockbridgeite and limonite.
Notable Occurrences include Cornwall, England; Ireland; Germany; Palermo Mine, New Hampshire and Pennington County, South Dakota, USA.
Best Field Indicators are crystal habit, color, associations, cleavage and streak.