The Mineral psilomelane
Psilomelane describes barium manganese
hydroxides that do not form in visible crystals. Originally recognized as an individual mineral species, Psilomelane was discredited by the
IMA in 1982. However, the name is still in use today, describing manganese hydroxides such as Romanechite and Hollandite that are not specifically identified and sometimes even admixed together.
Psilomelane can be
banded with Pyrolusite, with alternating layers of light and dark gray bands. It is named after the Green term "
psilos", meaning smooth, and "
melas", meaning black.
Chemical Formula
BaMn2+Mn4+8O16(OH)4
Crystal System
Monoclinic
Uses
Psilomelane is an ore of manganese. The banded form combined with Pyrolusite is sometimes polished as a collectors species and as a minor gemstone.
Noteworthy Localities
Psilomelane occurs in many manganese deposits worldwide, often in uninteresting forms. Only few localities have produced any remarkable specimens. Fuzzy, hair-like masses associated with Pyrolusite form a very unique habit from the Tower mine, Luis Lopez Manganese District, Socorro Co., New Mexico. Specimens have also been found in Taouz, Er Rachidia Province, Morocco; Ironwood, Gogebic County, Michigan; Bisbee, Cochise Co., Arizona; and Austinville, Wythe Co., Virginia.
Common Mineral Associations
Barite, Pyrolusite, Quartz, Hematite
Distingushing Similar Minerals
Pyrolusite - Most commonly in crystallized aggregates, which are lacking in Psilomelane.