These calcite specimens were found in a pocket in the El Americano (Can Sala) mine-quarries, in the Montseny mountains. This big geode was called "Mercedes" due to the curious color zoning that can be observed at the terminal rhombohedrons faces reminiscent of the German automobile company logo.
Crystals appeared partially coated by carbonated iron oxides and sometimes showed a complex prism, sometimes growing on scalenohedral crystals (like this specimen). This calcite shows a intense fluorescence under UV light. These pieces have disappeared from the market.