Melanterite, quartz

Here's a blueish/green metallic grey cluster of melanterite crystals atop of quartz. Melanterite is a hydrated iron sulphate formed after the decomposition of pyrite or other iron minerals due to the action of surface waters. It is often found in mines as a post-mining formation on mine walls. Rarely in nice crystals like this! With minimal damage to the crystal "flower", it is a nice specimen. From the collection of Kay Robertson and is accompanied by her label plus an older hand-written label.