The Collaborative International Dictionary of English v.0.48:

Covelline \Co*vel"line\ (k?-v?l"l?n), Covellite \Co*vel"lite\
   (-l?t), n. [After Covelli, the discoverer.] (Min.)
   A native sulphide of copper, occuring in masses of a dark
   blue color; -- hence called indigo copper.
   [1913 Webster]