Troctolite

Troktolith (also Troctolith trout or stone) is a rock from the group of mafic plutonic rocks.

Description of rock and mineral composition

The mineral composition comprises plagioclase ( labradorite and Bytownite ), olivine, up to 5% pyroxene and biotite in small amounts, hornblende, magnetite and sulfide ore minerals, but never quartz. With this composition Troktolithe belong to the group of gabbroic, although they contain significantly more olivine pyroxene instead. Troktolithe are often medium to coarse grained and have a characteristic mottled appearance, which is caused by the dark green olivine in a bright plagioclase matrix. Due to the dotted appearance of the rock masons was called trout stone.

Origin and Occurrence

Similar to gabbro come Troktolithe before as components of oceanic crust and are found as a result of autopsy in collisional orogens. They also occur in layered intrusions along with other gabbroic and ultramafic rocks in the continental crust. Examples are the Bushveld complex in South Africa or the Stillwater Complex in Montana. In Germany you will find Troktolithe in resin as part of the Harzburg gabbro.

Troktolithe were also found on the moon.