Pyrolusite

• Weichmanganerz

Pyrolusite, also known as Weichmanganerz or chemically as manganese ( IV) oxide, is a common mineral of the mineral class of " oxides and hydroxides ." It crystallizes in the tetragonal crystal system with the chemical composition of MnO 2 and mostly forming dendritic, stalactitic, grape-like, granular or powdery masses of dark gray to black in color. Under favorable conditions of formation also prismatic, acicular, striped crystals can develop, which are up to eight inches tall.

Special Features

Pyrolusite is infusible before the blowpipe, but gives off oxygen. If a borax bead used, they turn blue. In hydrochloric acid pyrolusite is soluble, with chlorine developed. In contrast to the very similar manganite, pyrolusite leaves on the dash panel a black line.

Etymology and history

The name of the Pyrolusits ​​was derived from the Greek words πυρος pyros for fire and λούω chosen lou washing, because it was used for stripping paint from glass.

Oxide Manganese ores have been known for a long time. 1822 shared an August Breithaupt in these three minerals, Weichmanganerz (later pyrolusite ), Glanzmanganerz (later manganite ) and bright Graumanganerz. The latter was called by him after further investigation Polianit. Wilhelm Ritter von Haidinger, however, found out that this is only a variety of Pyrolusits ​​.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the pyrolusite belonged to the department of " oxides with the molar ratio of metal: oxygen = 1: 2 ( MO2 and related compounds ) ," where he along with Argutit, cassiterite, paratellurite, Plattnerit, rutile and Tripuhyite the " Rutilgruppe " with the system no. IV/D.02 formed.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the pyrolusite also in the department of " oxides with the ratio of metal: oxygen = 1: 2 and comparable " one. However, this is further divided according to the relative size of the involved cations and the crystal structure, so that the mineral according to its composition in the subsection "With medium-sized cations: chains of edge-sharing octahedra " is to find where it together with Argutit, cassiterite, Plattnerit, rutile, Tripuhyite, Tugarinovit and Varlamoffite the " Rutilgruppe " with the system no. 4.DB.05 forms.

The mainly common in English-speaking classification of minerals according to Dana assigns the pyrolusite in the class of " oxides and hydroxides " and there in the department of " oxides ". Here he is with Argutit, Ilmenorutil, cassiterite, Plattnerit, rutile, Squawcreekit, stishovite and Struverit in the " Rutilgruppe ( Tetragonal: P4/mnm ) " with the system no. 04:04:01 to find within the sub-division of "simple oxides with a cation charge of 4 ( AO2 ) ".

Modifications and varieties

The compound MnO2 is trimorph, meaning they crystallized in tetragonal symmetry except as pyrolusite still in hexagonal symmetry as Akhtenskit and orthorhombic symmetry as ramsdellite.

There are two known varieties of Pyrolusites. These are the morphological variety Polianit, which is a pseudomorph of pyrolusite and manganite by a silver-bearing variety.

Education and Locations

Pyrolysite formed under strongly oxidizing, hydrothermal conditions in manganese ores. Furthermore, the mineral can form in swamps and shallow lakes, as well as a weathering product of manganite. It is associated with manganite, hollandite, hausmannite, Braunite, Chalkophanit, goethite and hematite.

Pyrolysite is a common manganese ore, there are many sites known. Among the best known include Elgersburg, Friedrichroda Oehrenstock in Thuringia, Eibenstock in Saxony, Giessen in Hesse, Oberroßbach and Bad Marienberg in Rhineland -Palatinate, Horni Blatna in the Czech Republic, Markhemville and Hillsborough in Canada, Ironwood, Leadville, Lake Valley and the Artillery Mountains in the United States. Manganese nodules exist to a considerable extent from pyrolusite.

Crystal structure

Pyrolusite crystallizes in the tetragonal crystal system in space group P42/mnm ( Raumgruppen-Nr. 136) with the lattice parameters a = 4.40 Å and c = 2.88 Å, and two formula units per unit cell.

Use

Pyrolusite is an important manganese ore for the extraction of the metal. It is also used as a black pigment for ceramics and glass.