from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A trigonal-ditrigonal pyramidal mineral containing aluminum, boron, hydrogen, magnesium, oxygen, silicon, and sodium.
from The Century Dictionary and Cyclopedia
- n. A brown to black magnesian variety of tourmalin, found in the Drave district in Carinthia.
Again, illite dominates in the great majority of samples, with a few samples containing kaolinite and dravite.
There is a trend running along the length of the property in which several samples are dominated by kaolinite, chlorite or dravite; these minerals tend to occur in the central parts of alteration systems.