Chromite is mined almost exclusively from massive to semimassive accumulations in ultramafic or mafic igneous rocks. Eluvial and alluvial deposits derived by the erosion of such rocks account for a small fraction of total production. Significant, but as yet unexploited, resources reside in laterites such as those of the Ramu River deposit in Papua New Guinea. Hard rock chromite deposits are normally assigned to one of two classes on the basis of deposit geometry, petrological character, and tectonic setting. Stratiform deposits are sheet-like accumulations of chromite that occur in layered ultramafic to mafic igneous intrusions. Podiform deposits are irregular but fundamentally lenticular chromite-rich bodies that occur within Alpine peridotite or ophiolite complexes . The Alpine peridotite or ophiolitic affiliation is an essential part of the latter definition: this has led to some confusion because some deformed stratiform deposits have morphological similarities to podiform deposits .