This mineral is found as a constituent of a variety of gabbro occurring on the shore at the village of Coverak, Cornwall. The rock is an aggregate of allotriomorphic grains of chrome-diopside, labradorite and olivine. The olivine is, in general, perfectly fresh, but it is traversed by a network of veins in which magnetite has been deposited. The whole of the iron-ore present in the rock occurs in these veins in the olivine ; so that in this, as in other respects, the rock bears a close resemblance to some of the gabbros described by Prof. Judd from the Western Isles of Scotland.