X-RAY SPECTROMETRY X-Ray Spectrom. (2008) Published online in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/xrs.1018 Preliminary data on the yellow ochers at the mine of Via Tirapelle in Verona (Italy) G. Cavallo 1* and R. Zorzin 2 1 University of Applied Sciences of Southern Switzerland, DACD-LTS, CH-6952 Canobbio, Switzerland 2 Museum of Natural History of Verona, Lungadige Porta Vittoria, 9 IT-37129 Verona, Italy Received 26 November 2007; Accepted 19 December 2007 The mine of Via Tirapelle in Verona is a paleokarst cave filled with insoluble material coming from the dissolution of the carbonatic formation; the size distribution generally belongs to the class of lime and clay. No more information is available on these natural earths. The analysis carried out in the past on these materials refer that the pigment was limonite. X-ray diffraction powder (XRD) analysis allows to refer that the yellow ocher is only the orthorhombic goethite. Goethite is locally associated with calcite, quartz and dolomite. Ankerite was found as a constituent of two samples deriving from the replacement of Fe inside the dolomite. X-ray fluorescence (XRF) analysis of major elements shows that the contents of Fe are related to goethite and ankerite, and to the poorly crystalline phases. Inductively coupled plasma emission spectrometry (ICP-ES) analysis of trace elements Cd, Co, Cr, Cu, Ni, Pb, Zn shows a linear correlation between Fe 2 O 3 and Cd, Cu, Ni, Zn. Copyright  2008 John Wiley & Sons, Ltd. INTRODUCTION Colour clay minerals 1 were widely used in the past as pigment being very stable in all the pictorial techniques and easily available; besides the exploitation and the production of the final pigment was really very simple. 2 A systematic study of these deposits located in the region of Veneto (Italy) started as part of a project on colours in the art. 3,4 This work intends to give a preliminary overview on the mineralogical and chemical composition of the clay materials collected in different areas of the main gallery of the mine located in Via Tirapelle in Verona, near the convex loop of the Adda river (Fig. 1). The analysis carried out by Federici in 1948 5 on these materials reported that the pigment was limonite with formula Fe 2 O 3 ž 3H 2 O; naturally limonite is not a mineral but a mix of iron oxyhydroxides where Fe 2 O 3 /H 2 O ratio is approximately 2/3. 6 This mine is the result of palaeokarstic phenomena (Miocene-Pleistocene), opening within the Priabona’s Marls; the origin is phreatic, followed by a vadose phase. The mine was filled by colouring earths (yellow and red) excavated in historical times. 7 Yellow ochers exhibit different appearance: generally, they are in the form of superimposed levels with thickness ranging from a few decimetres to a few centimetres; another form looks like the spots on a leopard and is concentrated on the walls, just near the entrance of the mine (Fig. 2). L Correspondence to: G. Cavallo, University of Applied Sciences of Southern Switzerland, DACD-LTS, CH-6952 Canobbio, Switzerland. E-mail: giovanni.cavallo@supsi.ch The colour of each level of the deposits is variable from yellow to brown; white and grey levels are also present. MATERIALS AND METHODS The description of the samples is reported in Table 1. X-ray diffraction (XRD) powder was used for studying the mineralogical composition of the collected samples. A diffractometer D8 Bruker; x-ray tube with Cu anti-cathode, Ni filter (Cu K˛ D 1.5418 ˚ A), generator settings 40 kV 40 mA was used. X-ray fluorescence (XRF) was used to determine the quantitative chemical composition of the major elements. Chemical composition is a complementary tool for XRD allowing to detect the presence and distribution of chemical elements linked to crystals and to partially crystalline compounds (i.e. oxides and hydroxides, siallitic alteration), very useful for this specific case. XRF analyses were performed on powder pills using a solution of elvacite 15% in acetone as binder. Elvacite is a polymer resin added in order to have the individual grains stick together. After acetone vaporizing, a grain- coated coagulate of grains is formed. 8 The grain size of the powder was less than 10 – 20 μm. 9 An automatic spectrometer Philips PW 1480; x-ray tube with Cr anode (70 kV, 30 mA) was used. Loss on ignition (LOI) contents were calculated as loss in weight upon heating at 1000 ° C after elimination of water of hydration at 110 ° C. The precision is better than 5%. Trace-element determination (Cd, Co, Cr, Cu, Ni, Pb, Zn) was carried out by inductively coupled plasma emission spectrometry (ICP-ES) using a Jobin-Yvon JY24 spectrometer. Copyright  2008 John Wiley & Sons, Ltd.