Definition of "manganese dioxide" []

• A black crystalline compound, MnO2, used as a depolarizer of dry-cell batteries and in textile dyeing. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Ayla reached for her amulet and felt for the fifth object she carried in it now: a piece of black manganese dioxide nestled in the small pouch along with the three nodules of iron pyrite stuck together, a red-stained oval of mammoth ivory, the fossil cast of a gastropod, and a chunk of red ochre."