from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. An isometric-hexoctahedral black mineral containing aluminum, iron, and oxygen.
from The Century Dictionary and Cyclopedia
- n. A mineral of the spinel group, containing alumina and iron, found in the Bohemian (Hercynian) Forest.
The black network within the fayalite crystals is of a second mineral, an iron-aluminum spinel called hercynite, that crystallized at the same time as the fayalite, giving rise to complex intergrowths of the two minerals.