• Webster's Revised Unabridged Dictionary
    • n Polianite (Min) Manganese dioxide, occurring in tetragonal crystals nearly as hard as quartz.
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Century Dictionary and Cyclopedia
    • n polianite Anhydrous manganese dioxid (MnO2), a mineral of a light steel-gray color and hardness nearly equal to that of quartz. It crystallizes in tetragonal forms, and is isomorphous with rutile (TiO2), cassiterite (SnO2), and zircon (ZrO2SiO2). It has often been confounded with the commoner mineral pyrolusite.
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Webster's Revised Unabridged Dictionary
Gr. to become gray