Népouite is a rare nickel which has the apple green colour typical of such compounds. It was named by E Glasser in 1907 after the place where it was first described (the type locality Commune, North Province , New Caledonia 2O )4, but most specimens contain some magnesium, and (Ni,Mg)3(Si2O5)(OH)4 is more realistic. There is a similar mineral called lizardite (named after the Lizard Complex, England) in which all of the nickel is replaced by magnesium, formula Mg3(Si2O5)(OH)4. These two minerals form a series; intermediate compositions are possible, with varying proportions of nickel to magnesium.
Pecoraite is another rare mineral with the same chemical formula as népouite, but a different structure; such minerals are said to be dimorphs of each other, in the same way as graphite is a dimorph of diamond. Népouite, lizardite and pecoraite are all members of the kaolinite-serpentine group
Garnierite ore that formed as a result of weathering of ultramafic rocks , and that occurs in many nickel deposits worldwide. It is a mixture of various nickel and magnesium (sheet silicates), including népouite. Associated minerals include calcite , chlorite, nontronite, sepiolite and willemseite.
As well as the type locality in New Caledonia, it has been found in Australia, Austria, the Czech Republic, the Democratic Republic of Congo, Germany, Greece, Italy, Japan, Morocco, Poland, Russia, South Africa and the US.