Nakauriite, Nakauri Mine, Japan
Mineral Matters #356
This week’s Facebook Mineral of the Week Group’s selected theme is Japanese minerals.
Many of the rarer species that you see from Japan are a bit dull and boring. But not nakauriite!
This species forms as vivid fibrous blue crystals on/in brucite-bearing serpentine. The formula is Cu8(SO4)4(CO3)(OH)6·48H2O, although, according to Mindat, the originally reported sulphate content appears to be questionable.
The Nakauri Mine is, as you expect, the Type Locality for nakauriite. The locality is also the Type Locality for asagiite, formula NiCu4(SO4)2(OH)6·6H2O, and interestingly, its pale blue-green colour is said to be unique enough to allow identification of the species! Not often you can say something like that!
This new mineral has been named asagiite after the traditional Japanese term ‘asagi–iro’, corresponding to the unique pale blue–green colour. The paper describing the colour gives the Red, Green and Blue (RGB) values that make up the colour. I have included a box generated with those values below the nakauriite image.
Below: Nakauriite, Nakauri Mine, Shinshiro city, Aichi Prefecture, Japan. Width of view 6mm. Click on the image below for a higher resolution version.
VERY confused!
I couldn't figure out what's supposed to be asagiite: It's not the nakauriite (bright blue), and the drab whatever in the middle doesn't seem worthy of note - and neither matches the color square, IIMHO.