Mineral Species: Pyrolusite

Chemical Formula: MnO2

Chemical Name: Managanese Oxide

Mineral Class: Oxide

Mineral Notes: Pyrolusite is the most common manganese mineral and is an important ore. The mineral rarely occurs alone and the term "wad" is used to indicate ores that are a mixture of several manganese oxides such as Pyrolusite, Psilomelane and others. Pyrolusite is an oxidation product of manganese minerals and often replaces Rhodochrosite, Rhodonite and Hausmannite. Pyrolusite has several interesting habits besides its common occurrence as dull, sooty, black masses. Possibly the most unusual is its dendritic habit that forms fern-like patterns on the surfaces of rocks such as sandstone. Another habit is its hair-like crystal aggregates that produce tufts of "hair of Pyrolusite fibers. Often specimens of pyrolusite are very difficult to distinguish from other manganese oxides.

Description: A brown matrix upon which sits a thick layer of black, earthy Pyrolusite. Embedded within this material are large, shiny, chunky crystals. However, examination under magnification shows that these are actually not individual crystals but aggregates of thin needle-like crystals of highly crystalline Pyrolusite. Some cluster into rounded rosette-like structures which are extremely lustrous. A super example of a uniquely pure form of Pyrolusite. The label says, recovered in 1980.

Location: Fullabrook Mine, Ifacombe, Devon, England.