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Manganese Dioxide

Pyrolusite powder, Manganese (greenish)

Chemistry MnO2 100.000

Significant Temperatures

• 535C: Decomposes to MnO

Links to Other Materials

• Manganese Carbonate - Unspecified
• Manganese Granular - Unspecified
• Manganese Oxide - Unspecified
• Cache

Hazards

• Manganese

Miscellaneous

• Family: Colorant
• Region: North America
• Mined At: Unspecified
• Raw Mineral: No
• Generic: Yes

Notes

Above 1080C, half of the oxygen disassociates to produce MnO, a flux which immediately reacts with silica to produce violet colors in the absence of alumina, browns in its presence. Thus if it is being used in glazes fired below 1080C it should be considered as MnO2, if above it should be taken as 81.5 MnO and 18.5 LOI.

Glazes and bodies that employ manganese dioxide below its conversion temperature of 1080C (to MnO) will fire black and purple colors. In glazes, it will behave in a refractory manner, stiffening the melt. Because to the expulsion of oxygen at 1080, glazes using manganese should avoid this temperature range to reduce the chance of blistering and ruining of the glaze surface.

This material is available as a pure material or as a ground ore (pyrolusite). Thus while generically it is pure MnO2 the actual name-brand materials may only be 75% MnO2.

Manganese dioxide is the key to Rockingham brown wares which are made by employing about 3% iron oxide and 7% manganese in a transparent lead glaze of a recipe such as: Feldspar 28, Kaolin 14, Flint 4, Lead bisilicate 40, Whiting 4.

Manganese browns have a different, often more pleasant character than iron browns.

Manganese oxides can occur in a number of less common forms: (i.e. Mn2O3, Mn3O4, Mn2O7).

Properties

• Body Color - Black

  When added to terra cotta bodies in amounts around 5% manganese dioxide will produce dark grey to black firing bodies.

• Glaze Color - Metallic

  Large amounts of manganese can produce metallic effects in a glaze. However, these glazes must not be used on food surfaces.

Data

• Specific Gravity: 4.9-5.0

Linked Articles

• Creativity and Illness by Dierdre O’Reilly

  A story of one persons struggle with manganese toxicity

• Manganese Inorganic Compounds Toxicology - Edouard Bastarache

  Manganese can be very toxic, expecially with regards to inhalation of the fumes during kiln firing. This material must be treated with care.

• Manganèse & Composés Inorganiques Toxicologie

  Manganèse & Composés Inorganiques Toxicologie - Edouard Bastarache

• My Story of Manganese and Parkinsons: Jane Watkins

  A person story about manganese poisoning.

• Potters Manganese Toxicity by Elke Blodgett

  A story of one persons struggle to identify and deal with manganese toxicity

Suppliers

• American Minerals Inc
  
• Generic
  

Authors

• Tony Hansen (Owner)

XML

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<material name="Manganese Dioxide" descrip="Pyrolusite powder, Manganese (greenish)" generic="1" rawmineral="0" searchkey="Mno2" loi="0.00">
<families>
<family name="Colorant"/>
</families>
<regions>
<region name="North America"/>
</regions>
<oxides>
<oxide symbol="MnO2" name="Manganese Dioxide" status="" percent="100.000" tolerance=""/>
</oxides>
<references>
<reference name="seealso" reason=""/>
<reference name="seealso" reason=""/>
<reference name="seealso" reason=""/>
</references>
<hazards>
<hazard name="Manganese"/>
</hazards>
<temperatures>
<temperature temperature="535C" notes="Decomposes to MnO"/>
</temperatures>
<suppliers>
<supplier name="American Minerals Inc" country="US" url="http://www.americanminerals.net" label=""/>
<supplier name="Generic" country="" url="" label=""/>
</suppliers>
<notes>
<note>Above 1080C, half of the oxygen disassociates to produce MnO, a flux which immediately reacts with silica to produce violet colors in the absence of alumina, browns in its presence. Thus if it is being used in glazes fired below 1080C it should be considered as MnO2, if above it should be taken as 81.5 MnO and 18.5 LOI.

Glazes and bodies that employ manganese dioxide below its conversion temperature of 1080C (to MnO) will fire black and purple colors. In glazes, it will behave in a refractory manner, stiffening the melt. Because to the expulsion of oxygen at 1080, glazes using manganese should avoid this temperature range to reduce the chance of blistering and ruining of the glaze surface.

This material is available as a pure material or as a ground ore (pyrolusite). Thus while generically it is pure MnO2 the actual name-brand materials may only be 75% MnO2.

Manganese dioxide is the key to Rockingham brown wares which are made by employing about 3% iron oxide and 7% manganese in a transparent lead glaze of a recipe such as: Feldspar 28, Kaolin 14, Flint 4, Lead bisilicate 40, Whiting 4.

Manganese browns have a different, often more pleasant character than iron browns.

Manganese oxides can occur in a number of less common forms: (i.e. Mn2O3, Mn3O4, Mn2O7).</note>
</notes>
<testdata>
<testitem testname="3" value="4.9-5.0"/>
</testdata>
</material>

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