Análise gemológica e de inclusões em berilos da região de Pedra da Onça - Santa Tereza- ES

Abstract

Abstract

Introduction: The studied beryls are aquamarine and heliodor of Pedra da Onça, district of Santa Teresa - ES, Brazil. The pegmatite is situated in the G5 suite of the eastern pegmatitic province, located in the Várzea Alegre massif, embedded in gneisses, paragneisses and ortogneisses. Objectives: To characterize 40 raw and 52 polished beryls as to their mineralogy, gemology, inclusions and optical discontinuities. Methodology: Collection, photographic records, characterization of pegmatite, gemological and immersion microscopic analysis, hydrostatic balance, polariscope, refractometer and magnifying glass. Results: Density values ​​and refractive index (IR) indicate that they are of different areas of the pegmatite, with inclusions of primary and secondary fluids, growth tubes and negative crystals with polyphase and melt type inclusions, fractions with single-phase fluid inclusions, negative crystals with polyphase inclusions, presence of growth lines and canaliculi with biphasic inclusions. Conclusion: The mineralogical analysis of the crude beryllium was consistent with the classical values, with the presence of central tube dissolutions aligned along the prism. The gemstones have a good classification, with total marks between 6 and 8 for color and 6 and 8 for purity, indicating excellent gemological potential for beryls from this deposit.