Niasite (red) with aerugite (green) and xanthiosite (yellow) on cotype specimen (LACMNH 74203); FOV 0.56 mm across. The image is published in an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( https://creativecommons.org/licenses/by/4.0/ ). — Photo: Anthony R. Kampf, Barbara P. Nash, Jakub Plášil, Jason B. Smith, and Mark N. Feinglosa · CC BY 4.0
Niasite
Niasite is an IMA-recognized mineral species in the arsenate class, with the chemical formula Ni²⁺₄.₅(AsO₄)₃.
It crystallizes in the tetragonal crystal system (space group I-42d). It is a member of the Jeffbenite structural group.
Key properties: Mohs hardness 4; specific gravity 5.245; Pale pink streak; Resinous to subadamantine luster; optically uniaxial.
IMA symbol Nia, IMA status: approved, named in 2020.
Secondary, likely formed from the breakdown of primary nickeline under dry (low relative humidity) and oxidizing (high oxygen fugacity) conditions.
It is found associated with Johanngeorgenstadtite, aerugite, bunsenite, quartz, rooseveltite, xanthiosite.
The name refers to the elements (excluding oxygen) in the mineral's composition: nickel (Ni) + arsenic (As).