The difference between Scoria and Slag

Scoria as a noun:

The slag or dross that remains after the smelting of metal from an ore.

Scoria as a noun (geology):

Rough masses of rock formed by solidified lava, and which can be found around a volcano's crater.

Slag as a noun:

Waste material from a coal mine.

Slag as a noun:

Scum that forms on the surface of molten metal.

Slag as a noun:

Impurities formed and separated out when a metal is smelted from ore; vitrified cinders.

Slag as a noun:

Hard aggregate remaining as a residue from blast furnaces, sometimes used as a surfacing material.

Slag as a noun:

Scoria associated with a volcano.

Slag as a noun (UK, pejorative, dated):

A coward.

Slag as a noun (UK, chiefly, Cockney, pejorative):

A contemptible person, a scumbag.

Slag as a noun (UK, pejorative):

A prostitute.

Slag as a noun (UK, Australia, New Zealand, South Africa, slang, pejorative):

A woman (sometimes a man) who has loose morals relating to sex; a slut.

Slag as a verb (transitive):

To produce slag.

Slag as a verb (intransitive):

To become slag; to agglomerate when heated below the fusion point.

Slag as a verb (transitive, sometimes with "off"):

To talk badly about; to malign or denigrate (someone).

Slag as a verb (intransitive, Australia, slang):

To spit.