### Mill leaching: a viable substitute for mercury amalgamation …

The material is crushed to −1/2 inch using dry stamp mills. Processing units have from 12 to 48 homemade steel ball mills (known locally as tromels) with diameter of 48 cm and length of 60 cm. One mill grinds 40 kg of ore for 4 h using 40 river pebbles (5–10 cm) or steel balls.

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