What is the meaning of Mullock?

Rubbish, waste matter.

Mining waste or ore processing waste:

  1. Overburden: waste material generated while searching for minerals or while mining, such as when sinking a shaft.
  2. Tailings: waste rock from which the wanted gold, minerals, opal, etc., has been extracted.

Overburden: waste material generated while searching for minerals or while mining, such as when sinking a shaft.

Tailings: waste rock from which the wanted gold, minerals, opal, etc., has been extracted.

Nonsense, rubbish.

A mess; the result of a blunder.

To clear waste material out of a mine.

Source: wiktionary.org