Green globular aggregates of the nikel sulphate mineral carrboydite from the type locality (Carr Boyd Ni Mine, Goongarrie, Western Australia, Australia) and only one of the three localities known worldwide. — Photo: David Hospital · CC BY-SA 4.0
Carrboydite
Carrboydite is an IMA-recognized mineral species in the sulfate class, with the chemical formula (Ni₁₋ₓAlₓ)(SO₄)ₓ/₂(OH)₂·nH₂O (x 3x/2).
It crystallizes in the hexagonal crystal system (space group P-3m1). It is a member of the Woodwardite, Hydrotalcite structural group.
Key properties: specific gravity 2.5; Dull to waxy. Color: Yellowish green, greenish yellow, blue-green, pale green, greenish blue luster; optically uniaxial.
IMA symbol Cby, IMA status: questionable, named in 1974.
A rare secondary mineral found in the oxidized zone of nickel sulfide deposits.
It is found associated with Malachite, azurite, paratacamite, brochantite, glaukosphaerite, takovite, nickeloan magnesite, chalconatronite, georgeite, halloysite, chabazite, gypsum.
The name refers to the Carr Boyd Rocks mine, Australia, the first known locality.