from The Century Dictionary.

  • noun A brown to black magnesian variety of tourmalin, found in the Drave district in Carinthia.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun mineralogy A trigonal-ditrigonal pyramidal mineral containing aluminum, boron, hydrogen, magnesium, oxygen, silicon, and sodium.


from Wiktionary, Creative Commons Attribution/Share-Alike License



  • Again, illite dominates in the great majority of samples, with a few samples containing kaolinite and dravite.

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  • 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.

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