The amphibolites of the Broken Hill district fall into two distinctive groups. One group, characteristically developed in the Broken Hill Basin, containscommon green hornblendeand lesser brown hornblende, and in places alman‐dine. These amphibolites are intimately associated with pyroxene‐brown horn‐blende‐bytownite granulites, in which hypersthene is the chief pyroxene. Every stage of transition can be recognized within the distances of a few feet.