Iocyanite

Iocyanite is a rare mineral with the chemical formula K2[Fe(CN)6]. It is a member of the cyanide group of minerals, which includes other compounds with the cyanide ion (CN-) as a significant component. Iocyanite is known for its distinctive deep blue color, which is a result of its iron(II) cyanide structure. It typically forms as a secondary mineral in the oxidation zone of copper deposits, often associated with other cyanide minerals such as copperas and malachite.

The mineral was first described in 1845 from the type locality of the Blue Bell mine in the Keweenaw Peninsula of Michigan, USA. It has since been found in a few other locations around the world, including the Kola Peninsula in Russia and the Broken Hill region in Australia. Iocyanite is not considered to be of significant economic importance due to its rarity and the fact that it is not a source of cyanide or iron.

Iocyanite crystals are typically small and prismatic, often forming in clusters or crusts. They are often found in association with other secondary minerals, such as malachite and azurite. The mineral is relatively soft, with a Mohs hardness of 3.5 to 4, and has a specific gravity of approximately 2.9. It is soluble in water and in dilute acids, which can lead to the formation of toxic hydrogen cyanide gas.

Iocyanite is of interest to mineral collectors and researchers due to its rarity and unique chemical composition. However, it is important to handle the mineral with care due to the potential for cyanide poisoning.