Mineralpedia Details for Cacoxenite

Named for the Greek words kakos, meaning “bad,” and xenizomenos, meaning “guest,” in reference to its presence in iron ores, which the phosphate content of the mineral degrades the quality of iron from the ore. Cacoxenite is an uncommon mineral in the broad sense, but is a common accessory in oxidized magnetite and limonite iron ore, and can also be found in iron and manganese bearing novaculites and in iron-rich sediment and soil. Localities for Cacoxenite are found in the Czech Republic, Germany, France, Ireland, Sweden, and the United States, among others. Orange, reddish orange, golden yellow, or brownish yellow acicular crystals in compact, concentric spherical to radial aggregates or coatings.

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

Formula

(Fe³⁺)₂₄AlO₆(PO₄)₁₇(OH)₁₂·75H₂O 

Crystal System

Hexagonal 

Crystal Habit

Radial, Acicular, Stellate 

Cleavage

None, None, None 

Luster

Silky 

Color

brownish yellow, green, yellow, golden yellow, red yellow 

Streak

yellow 

Class

Hexagonal - Dihexagonal Dipyramidal 

Fracture

Uneven 

Hardness

3-3.5 

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Golden acicular crystals in tiny 1mm and less radial balls.

Stunning golden brown, acicular radial sprays of Cacoxenite to 1mm.

Sprays of golden Cacoxenite to about 1mm well protected in a seam 6cm long and 1.5cm wide.

Golden fibrous sprays to 1mm.

Golden acicular sprays to about 0.75mm lining vugs.

Golden straw-like colored radial sprays of Cacoxenite to 0.5mm.

Gold-yellow thin botryoidal Cacoxenite totally covering one side of black Shale matrix.

Small orange sphericules of Cacoxenite less than 1mm.

Cacoxenite as a thin orange film alteration over light green botryoidal Kidwellite and Dufrenite crystals to 4mm.

Sprays of Cacoxenite to 1mm.

Golden yellow sprays to 1mm.

Golden spherules and fibrous sprays of Cacoxenite with purple balls of Strengite.

Golden fibrous hairs of Cacoxenite.

Radial sprays of orange Cacoxenite to almost 1mm.

Special Info

Specimen & Photo of: Henry Barwood Professor, Earth Science Department of Chemistry and Physics Troy University

The first two photos are those by Dr. Henry Barwood. Micro Cacoxenite fibers with well formed prisms and pyramidal terminations. FOV is about .6  X .4mm. Imaged with a Canon 40D, 23mm Nikon objective and 300mm Canon FD telephoto in a tube configuration and stacked using Combine Z software.

The second set were taken by Tom Loomis: Cacoxenite sprays to about 0.75mm. There is thick, rich coverage like carpet in places and also singular sprays throughout.

Golden fibrous hairs of Cacoxenite in iron ore matrix of Hematite. Uncommon, at least on the market for this locality.