Hokkaidoite

Mineral Matters #477

Given that I will be in Japan very soon, I thought I’d post something Japanese!

Hokkaidoite is a recently described new mineral from the Hokkaidō Prefecture, Japan, approved as IMA No. 2022-104, but still pending publication.

Mindat describes it as an organic mineral, most likely a Polycyclic Aromatic Hydrocarbon (PAH).

Hokkaidoite is composed of benzo[ghi]perylene, an organic compound made up of carbon and hydrogen. It is found in opals formed by old hot springs in Shikaoi-chō, Hokkaidō, and as pale-yellow plate-like crystals in quartz veins in Aibetsu-chō. One of its unique features is its brilliant yellow to yellowish-green fluorescence when exposed to ultraviolet light.

Specimens of hokkaidoite are displayed at the Tokachi Shikaoi Geopark Visitor Centre, the Hokkaidō University Museum, and the Higashitaisetsu Nature Center.

This specimen may or may not have been analysed. I don’t know. It could be just opal! Also, I have it on good authority that the hokkaidoite is not found at Shikaribetsu Lake, the locality shown in Mindat.

Below: Hokkaidoite (as labelled), Opal, Shikaribetsu Lake, Shikaoi (Shikaoi-Chō), Kato District, Tokachi Subprefecture, Hokkaidō Prefecture, Japan. Width of specimen 17mm.