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.
	3.	Waste matter; any worthless matter separated from the better part; leavings; dregs; refuse. All world's glory is but dross unclean. - Spenser. At the devil's booth are all things sold, Each ounce of dross coats its ounce of gold. - Lowell.

Noun	1.	dross - worthless material that should be removed; "there were impurities in the water" Synonyms: impurity
	2.	dross - the scum formed by oxidation at the surface of molten metals Synonyms: scoria, slag

alluvion, alluvium, ash, ashes, brand, calx, carbon, charcoal, cinder, clinker, coal, coke, coom, deposition, deposits, diluvium, draff, ember, feces, froth, fume, grounds, lava, lees, loess, moraine, offscum, precipitate, precipitation, reek, scoria, scum, sediment, settlings, silt, sinter, slag, smoke, smudge, smut, soot, sublimate, sullage