Caracterização Mineralógica do Corpo Pegmatítico “Azurite" em Araçuaí (MG)

Abstract

The northern region of Minas Gerais is known for its great geotectonic and geological diversity, mainly due to its wide range of pegmatites, some of which are lithium-bearing. The Brazilian Eastern Pegmatite Province traverses the state in a NNE-SSW orientation, encompassing the municipality of Araçuaí. This study aims to analyze and characterize a pegmatitic body located on the margins of Chapada do Lagoão, in the rural area of Araçuaí, Minas Gerais, through collected samples, along with the preparation of petrographic thin sections. The rock massif is locally known as "Azurite" due to the large quantity of blue minerals within the pegmatite, interpreted as azurite crystals. However, there is no local or regional literature describing pegmatites containing azurite. Based on physical property tests, it was initially determined that the mineral in question was not azurite. To confirm this conclusion and accurately identify the mineral, macroscopic descriptions of the samples were conducted, followed by microscopic analyses using petrographic thin sections under an optical microscope. As the mineral could not be identified through optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were employed for further investigation of the blue mineral. Through SEM-EDS analyses, it was concluded that the blue mineral is an iron phosphate, identified as vivianite (Fe²⁺Fe²⁺₂(PO₄)₂·8H₂O), rather than a copper carbonate, azurite (Cu₃(CO₃)₂(OH)₂).