Dross /(drŏs; 115)/

Dross

n.
  1. The scum or refuse matter which is thrown off, or falls from, metals in smelting the ore, or in the process of melting; recrement.
  2. Rust of metals. [R.]
  3. Waste matter; any worthless matter separated from the better part; leavings; dregs; refuse.
    All world's glory is but dross unclean.
    At the devil's booth are all things sold, Each ounce of dross coats its ounce of gold.