Periclase is a magnesium mineral that occurs naturally in contact metamorphic rocks and is a major component of most basic refractory bricks.

The type locality is Monte Somma, Somma-Vesuvius Complex, Naples Province, Campania, Italy.

[5] In addition to its type locality, it is reported from Predazzo, Trentino, Italy; Carlingford, County Louth, Ireland; Broadford, Skye and the island of Muck, Scotland; León, Spain; the Bellerberg Volcano, Eifel district, Germany; Nordmark and Långban, Varmland, Sweden; and Kopeysk, southern Ural Mountains, Russia.

As a consequence, the physical properties of periclase are well known, which makes the mineral a popular standard in experimental work.

[8][9] At the bottom of the transition zone of the mantle, the reaction transforms γ-olivine into a mixture of perovskite and ferropericlase and vice versa.