from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. manganese dioxide, occurring in hard tetragonal crystals
from the GNU version of the Collaborative International Dictionary of English
- n. Manganese dioxide, occurring in tetragonal crystals nearly as hard as quartz.
from The Century Dictionary and Cyclopedia
- n. Anhydrous manganese dioxid (MnO2), a mineral of a light steel-gray color and hardness nearly equal to that of quartz.
Ancient Greek to become grey. (Wiktionary)