Troctolite /ˈtrɒktəlaɪt/ (from Greek τρώκτης 'trout' and λίθος 'stone') is a mafic intrusive rock type.

It consists essentially of major but variable amounts of olivine and calcic plagioclase along with minor pyroxene.

However, unlike gabbro, no troctolite corresponds in composition to a partial melt of peridotite.

Thus, troctolite is necessarily a cumulate of crystals that have fractionated from melt.

[1] Troctolite is found in some layered intrusions such as in the Archean Windimurra intrusion of Western Australia, the Voisey's Bay nickel-copper-cobalt magmatic sulfide deposit of northern Labrador,[2] the Stillwater igneous complex of Montana, the Duluth Complex of the North American Midcontinent Rift,[3] and the Tertiary Rhum layered intrusion of the island of Rùm, Scotland.