Matéria (Rio de Janeiro) On-line version ISSN 1517-7076 Materia (Rio J.) vol.17 no.3 Rio de Janeiro 2012 http://dx.doi.org/10.1590/S1517-70762012000300004                                       !    "  # $  I Universidade Federal do Rio de Janeiro, Institute of Chemistry. Avenida Athos da Silveira Ramos, 149 Bl / 7 ° andar, CEP 21941&909, Cidade Universitaria, Rio de Janeiro, RJ. email: asoeiro@cetem.gov.br ; chico@iq.ufrj.br ; martam@iq.ufrj.br II Centre for Mineral Technology, Av. Pedro Calmon, cep 21941&908 900, University City Rio de Janeiro, RJ. email: jsampaio@cetem.gov.br %&’& Potassium is one of the major macronutrients present in the soil. However, in Brazil it becomes scarce due to high acidity of soils. Thus, the demand for alternative sources of potassium grows considerably. In this context, the chemical and mineralogical characterization of verdigris Cedars Abaeté, Minas Gerais was performed, as well as an evaluation of the thermal treatment of the same with or without the addition of CaO, in order to solubilize the potassium present in the rock. The characterization of the rock was developed by the techniques of X&ray diffraction (XRD), X&ray fluorescence (XRF) and infrared spectroscopy (IR). The evaluation results of the XRF showed that the rock has 6.95 mass% of K2O, related to the presence of glauconite. This was confirmed by XRD, due to the presence of characteristic peaks at 1.00; 0.45; 0.24 and 0.15 nm, and the occurrence of IR bands at 3520, 3440, 1020 and 630 cm&1. There are also high levels of SiO2 (64.65%), indicative of the presence of quartz, which is characterized by an intense peak at 0,335 nm. In the heat treatment step, verdigris was heated for 2 hours at a temperature of 1200 ° C. To increase the solubility of the potassium present in the rock, the reaction with calcium oxide in proportions of 10, 20 and 30% by mass was performed. The structural changes in the rock were followed by XRD and IR. It was observed the reaction between the rock and calcium oxide, changes were observed in the Si&O stretching position characteristic bands in IR, around 1100 cm &1 and the disappearance of peaks of X&ray diffraction related to glauconite. The reaction with 20% CaO allowed an extraction of 7.7% of the potassium in the sample. () Verdete, termopotássio, glauconite, slow&release fertilizer.