This specimen is Goethite on Zeolite geode 74*85*77mm from Madagascar weighing 487g. It is highly unusual. I have not been able to verify that the pink mineral is Goethite, as claimed by my generally reliable supplier. Goethite is not normally pink. The pink minerals other features do match with Goethite.
Goethite is a common iron oxide mineral with the chemical formula FeO(OH). Goethite typically forms as prismatic or needle-like crystals, as in this specimen. It al;so forms in massive, botryoidal, radial and stalactitic forms. It also forms as encrustations or pseudomorphs, where it replaces and takes on the form of a previously present mineral.
Goethite can be banded or iridescent. Goethite has a range of colors, including yellow-brown, reddish-brown and dark brown. Impurities and the other minerals present also influence its colour.
Geothite itself is not UV reactive; however, the unusual combination of minerals present in this specimen does strongly react to ultra-violet light.
