Goethite after Pyrite

specimen number:
2063181

location:
Queen location, Guadalupe Mts., Eddie Co., New Mexico, USA

description:
A grouping of sharp cubic pyrite crystals with no points of attachment. These are completely replaced with lustrous brown goethite. In perfect condition all around. The specimen comes with a previous label from the collection of Ray DeMark, he collected the piece on April 26, 2003.

Goethite after pyrite is a pseudomorph where the original iron sulfide mineral is chemically altered and replaced by iron oxyhydroxide. Throughout this oxidation process, the crystal preserves the sharp cubic, pyritohedral, or octahedral geometry of the precursor pyrite, while its metallic brass-yellow luster transforms into a rich brown, yellowish-brown, or blackish-brown earthy finish. These specimens are highly valued by collectors for maintaining pristine crystal habits despite complete mineralogical replacement.

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