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The Mineral pyrolusite

Curving Radiating Pyrolusite Crystals

Pyrolusite is the most common manganese mineral. It is one of several manganese oxide minerals, which are all dark gray to black in color and may be very difficult to distinguish from one another, especially when in massive form. Wad is a term used to describe a combination of several unidentified manganese oxides, which may include a combination of Pyrolusite, Manganite, Psilomelane, and Romanechite.

Pyrolusite is known for its finely fibrous acicular crystal habits. These forms are usually sooty and will likely smudge the hands when touched.

Pyrolusite is named from a combination of the Greek words "Pyr" - fire, and "Louein" - to wash, since this mineral was once used as an agent to remove green and brown tints during the manufacture of glass.

Chemical Formula

MnO2

Color

Dark gray to black, sometimes with a bluish tint

Crystal System

Tetragonal

Properties

Streak
Bluish black to black
Hardness
6 - 6.5
Transparency
Opaque
Specific Gravity
4.4 - 5
Luster
Metallic, dull
Cleavage
1,1
Fracture
Splintery, uneven
Tenacity
Brittle
Other ID Marks
Leaves black powdery residue upon contact with surfaces.

Crystal Habits

Individual crystals are rare, and when they do occur, they are in thin, sharp crystals with steep triangular edges or rectangular blocky crystals. Crystals are usually deeply striated or etched in parallel lines. Large crystals are more often pseudomorphs of Pyrolusite after Manganite. More commonly in finely packed fibrous, acicular and radial forms composed of very fine needles or fibers. Also in intersecting radiating veins, in bladed groups, reniform, botryoidal, [statalctitic%] grainy, massive, concretionary, and earthy.

3D Crystal Atlas

Additional Information

Composition
Manganese dioxide
In Group
Oxides; Simple Oxides
Striking Features
Crystal habits, streak, and powdery residual
Environment
In the oxidized zone of hydrothermal replacement deposits, and in acid-rich bogs as an alteration product.
Rock Type
Igneous, Sedimentary, Metamorphic

Varieties

 -   Uncommon form of Pyrolusite that has larger, individual crystals.

Uses

Pyrolusite is one of the most important ores of manganese. It is also a component of the production of steel, and was once used for the manufacture of batteries. It is also used in the preparation of chlorine, and as an agent in coloring and dyes.

Noteworthy Localities

Pyrolusite is a very common mineral worldwide. However, most forms are in uninteresting massive and earthy habit. Only localities that produced specimens worthy of collections are mentioned here.

Some of the best Pyrolusite specimens have come from the Imini mine, Ouarzazate Province, Morocco, in the form of lustrous crystal sprays. Many localities in Germany produce good examples of Pyrolusite. Especially noteworthy are are Ilfeld, Nordhausen, Harz Mountains, Thuringia; and Gremmelsbach, Triberg, Black Forest, Baden-Württemberg. Micro crystal tufts come from the Clara Mine, Oberwolfach, Black Forest, Baden-Württemberg.

Rounded crystal groups and bladed aggregates of Pyrolusite have come from Cartagena Mountains, Murcia, Spain; and sharp crystal sprays from Serra da Mina Mine, Cercal, Setúbal District, Portugal. Relatively large crystals of Pyrolusite came from the Iron Monarch Quarry, Iron Knob, South Australia. Most crystallized Pyrolusite from this locality is actually a pseudomorph after Manganite.

In the U.S., an unusual type of Pyrolusite in groupings of uniquely large crystals is known from Las Cruces, Doña Ana Co., New Mexico. Other important U.S. localities include the Taylor Mine, Alberta, Baraga Co., Michigan; and Negaunee, Marquette Co., Michigan.

Common Mineral Associations

Hematite, Calcite, Quartz, Limonite, Manganite, Psilomelane, Goethite, Rhodonite

Distingushing Similar Minerals

Psilomelane, Romanechite and other manganese oxides - May be very difficult to distinguish, although they don't often form in the lustrous compact crystal groups as Pyrolusite.
Manganite - Does not powder the finger upon contact.
Hematite (when reniform or botryoidal) - Slightly attracted to magnetic fields, has a red streak.
Goethite - Usually has a duller luster, doesn't smudge the hands.


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