To salt a mine

from The Collaborative International Dictionary of English v.0.48
Salt \Salt\, v. t. [imp. & p. p. {Salted}; p. pr. & vb. n.
   {Salting}.]
   1. To sprinkle, impregnate, or season with salt; to preserve
      with salt or in brine; to supply with salt; as, to salt
      fish, beef, or pork; to salt cattle.
      [1913 Webster]

   2. To fill with salt between the timbers and planks, as a
      ship, for the preservation of the timber.
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   {To salt a mine}, to artfully deposit minerals in a mine in
      order to deceive purchasers regarding its value. [Cant]

   {To salt away}, {To salt down}, to prepare with, or pack in,
      salt for preserving, as meat, eggs, etc.; hence,
      colloquially, to save, lay up, or invest sagely, as money.
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