Difference Between Pyrolusite and Psilomelane

The key difference between pyrolusite and psilomelane is that pyrolusite has a tetragonal crystal system, whereas psilomelane has a monoclinic crystal system.

Pyrolusite and psilomelane are two different minerals containing manganese atoms. Although both are oxide minerals, we can easily identify the difference between pyrolusite and psilomelane by their appearance.

CONTENTS

1. Overview and Key Difference
2. What is Pyrolusite 
3. What is Psilomelane
4. Side by Side Comparison –  Pyrolusite vs Psilomelane in Tabular Form
5. Summary

What is Pyrolusite?

Pyrolusite is an oxide mineral mainly consisting of manganese dioxide. It is an important ore for manganese metal. This mineral substance appears in dark black to lighter gray, sometimes bluish, depending on the impurities present in this mineral. The crystal system of this mineral is tetragonal, and the chemical formula can be given as MnO2. This mineral often has an amorphous, granular, fibrous or columnar structure which sometimes form reinform crusts. Moreover, this mineral has a metallic luster. The streak color of this mineral is bluish-black, and it soils the fingers. Furthermore, the mineral is opaque.

Figure 01: Pyrolusite Mineral

Pyrolusite mineral occurs in association with manganite, hematite, hausmannite, braunite, and hollandite. This substance also occurs in bogs and often result from alteration of manganite. More importantly, pyrolusite is among the most common manganese minerals.

There are different uses of pyrolusite, including the extraction of manganese metal via the reduction of the mineral with sodium, magnesium, or aluminum, or via electrolysis. This mineral is commonly used for the manufacture of spiegeleisen and ferromanganese and for the production of many alloys such as manganese-bronze alloy. It is also useful as an oxidizing agent in the preparation of chlorine gas.

What is Psilomelane?

Psilomelane is an oxide mineral mainly consisting of barium, potassium and manganese oxide compounds. It appears in black color and contains gray pyrolusite bands. This substance has a monoclinic crystal system and conchoidal fracture. Furthermore, this mineral has a sub-metallic luster which has a dull appearance, and the mineral streak color is brownish-black. The general chemical formula for this mineral can be given as Ba(Mn2+)(Mn+4)8O16(OH)4. However, we cannot give a definite chemical composition for this substance.

Figure 02: Psilomelane Mineral

When considering the occurrence of psilomelane, it is a common and important ore of manganese which occurs under the same conditions and has the same commercial applications as well.

What is the Difference Between Pyrolusite and Psilomelane?

Both pyrolusite and psilomelane are oxide minerals. The key difference between pyrolusite and psilomelane is that pyrolusite has a tetragonal crystal system, whereas psilomelane has a monoclinic crystal system. Furthermore, pyrolusite has a metallic luster, while the luster of psilomelane is sub-metallic. They have different streak colors as well; e.g. streak color of pyrolusite is black to bluish-black color, while the streak color of psilomelane is brownish black. Both these minerals are opaque in their optical character.

Moreover, pyrolusite is used for the extraction of manganese metal, manufacture of spiegeleisen and ferromanganese and the production of many alloys such as manganese-bronze alloy, while psilomelane is mainly used for the extraction of manganese metal.

The following infographic tabulates the differences between pyrolusite and psilomelane.

Summary – Pyrolusite vs Psilomelane

Pyrolusite and psilomelane are important mineral ores of manganese metal. However, the composition and structure of manganese oxide in these substances are different from each other. The key difference between pyrolusite and psilomelane is that pyrolusite has a tetragonal crystal system, whereas psilomelane has a monoclinic crystal system.

Reference:

1. “Pyrolusite.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., Available here.

Image Courtesy:

1. “Mineraly.sk – psilomelan” (CC BY 2.0) via Commons Wikimedia
2. “Pyrolusite – USGS ID Stose, GW 1425” By Unknown author – (Public Domain) via Commons Wikimedia

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