This specimen provides a great opportunity to acquire an exceptionally rare species from a world-famous yet seldom seen locality, the Rio Tinto mine in Andalusia, Spain. An excellent crystallised specimen of the lead-arsenic sulphosalt Gratonite, ex-matrix and composed from perfect, sharply defined Gratonite crystals intermixed with granular Gratonite. The trigonal crystals attain at least 5 mm and line the vuggy interior and external faces of this highly porous small miniature (or large thumbnail). The Gratonite is a sooty dark grey to black with a dull to metallic lustre. It's great to see a specimen from the Rio Tinto mines, a locality I visited forty five years ago and have fond memories of. This rare sulphosalt is from the Dr Josef Clemente Collection of southern Germany and comes with a 'Museo Mineralogico of Madrid' label.
