having a metallic luster and thin foliated structure. Occurrences Diallage is commonly found in association with other members of the augite series within the clinopyroxenes, such as with fassaite. It can also be found with other minerals, such as olivine, biotite and hornblende. It is a deep-seated igneous (also known as magmatic) mineral, and it is intrusive, meaning it crystallizes below the Earth's surface, and the slow cooling allows the crystallization to occur. It usually grows in basic igneous rocks like gabbros and peridotite, and in low-grade metamorphic rocks such as metagabbros. Furthermore, diallage is an essential constituent of gabbros. It can also occur in serpentines, but rarely ever in schists and basalt. Localities Typically, this mineral can be found in Europe, and is mostly common in Italy. In Romania, it can be found in the area of Svinița in gabbros, and in peridotites near Szarvaskő in Hungary. It can be found basically anywhere in Italy where there are basic igneous rocks and/or low-grade metamorphic rocks. It can also be found in the western region of the Alps, around Sondalo, however these specimens are generally lower quality ones. Higher grade specimens occur in Trento, and in a few spots of the Ligurian Apennines. These spots include Passo del Bracco, the mines of Acquafredda and Bargone, next to Sestri Levante. Another occurrence is in the Tuscan-Emilian Apennines, in Sasso Puzzino and Serra del Zanchetto, near Bologna. Other than these, diallage also occurs in Austria, Germany, and in the Polish Silesia as well. Controversies Although it was supposed to be a legitimate variant of diopside, gemdat.org claims diallage to be a 19th-century name variant of some stones of the amphibole and pyroxene groups. The site also claims that most specimens under this name are either hypersthenes or diopsides. However, pseudohyperstene is also a synonym for diallage, therefore it is not a hypersthene, as pseudo means not genuine. Furthermore, opinions whether it is a distinct species or a variant differ. Even the reason for why it's a variant, or which mineral's variant it is, differs. Mindat claims it is a variant since the parting is different, while Wiktionary states that it is a green variety of pyroxene. Britannica claims diallage to be either of the pyroxenes augite and diopside. Furthermore, the formula of the mineral differs from site to site. On the Hungarian Wikipedia, diallage has the formula of Ca7Fe2+Mg6Fe3+Al(Si14Al2O48), while on mindat.org