The Collaborative International Dictionary of English v.0.48:

Elvan \Elv"an\, a.
   1. Pertaining to elves; elvish.
      [1913 Webster]

   2. (Mining) Of or pertaining to certain veins of feldspathic
      or porphyritic rock crossing metalliferous veins in the
      mining districts of Cornwall; as, an elvan course. Elvan

The Collaborative International Dictionary of English v.0.48:

Elvan \Elv"an\, Elvanite \Elv"an*ite\, n.
   The rock of an elvan vein, or the elvan vein itself; an elvan
   course.
   [1913 Webster]