Stunning Cacoxenite Crystals

Cacoxenite Crystals
Stunning Cacoxenite Crystals. From: La Paloma Mine, Zarza la Mayor, Cáceres, Extremadura, Spain. Photo: Rewitzer Christian


Cacoxenite was first described in 1825 for an occurrence in the Hrbek Mine, Bohemia, Czech Republic. It occurs as a secondary phase in oxidized magnetite and limonite deposits. It also occurs in novaculites and in iron and phosphorus rich sediments.

Often times, it forms as fuzzy brownish yellow, brown, yellow, or gold radiated tufts or strands. It may also appear as reddish orange or greenish yellow. The cacoxenite is occasionally referred to cacoxene or cacoxitite.

Formula: Fe3+24Al(PO4)17O6(OH)12·17(H2O)
System: Hexagonal
Colour: Yellow to brownish ...
Hardness: 3 - 4

Cacoxenite forms as a secondary mineral within oxidized iron deposits. Iron-rich solutions leach phosphorus from surrounding rocks, and upon encountering aluminum, precipitate as cacoxenite crystals. These crystals often form as radiating tufts or star-like clusters, exhibiting a vitreous to silky luster.

Despite its name, cacoxenite has limited application in iron smelting due to its low abundance and detrimental effect on iron quality. However, its unique combination of color, morphology, and rarity makes it a sought-after mineral by collectors.


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