Adelite
The rare mineral adelite, is a calcium, magnesium, arsenate with chemical formula CaMgAsO4OH. It forms a solid solution series with the vanadium bearing mineral gottlobite. Various transition metals substitute for magnesium and lead replaces calcium leading to a variety of similar minerals in the adelite - duftite group.
Adelite forms variably colored (blue, green, yellow and grey) crystals in the orthorhombic crystal system. The form is typically massive. It has a Mohs hardness rating of 5 and a specific gravity of 3.73 to 3.79.
It was first described in 1891 from Värmland, Sweden. Its name comes from the Greek word for indistinct.