An autogenous mill is a self-grinding mill. Larger pieces of ore are used as grinders. For this purpose larger and medium-sized pieces of ore are separated from the crushed ore, already at the crushing stage. The Keretti mine had separate silos for larger and medium-sized pieces of ore.

An autogenous mill operates mainly by grinding the ore pieces against each other, whereas rod and ball mills operate mainly by dropping the grinders onto the ore. In an autogenous mill, grinding is also done to a lesser extent by dropping the grinders onto the ore.

Autogeenimyllyn jauhaminen perustuu siihen, että malmikappaleet hioutuvat toisiaan vasten, siinä missä tanko- ja kuulamyllyt jauhavat malmia pääasiallisesti tiputtamalla jauhinkappaleet sen päälle. Vähemmässä määrin myös autogeenimyllyssä tapahtuu jauhaminen tiputtamalla jauhinkappaleet malmin päälle.