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Title: Depósitos de alexandrita de Malacacheta, Minas Gerais.
Authors: Basílio, Márcio Silva
Soares, Antônio Carlos Pedrosa
Evangelista, Hanna Jordt
Issue Date: 2000
Citation: BASÍLIO, M. S.; SOARES, A. C. P.; EVANGELISTA, H. J. Depósitos de alexandrita de Malacacheta, Minas Gerais. Geonomos, Belo Horizonte, v. 8, n.1, p. 47-54, 2000. Disponível em: <>. Acesso em: 20 de jun. 2017.
Abstract: Since 1975, alexandrite [Be(Al2-xCrx)2O4], the chromium-bearing crysoberyl variety, has been exploited from alluvial and paleo-alluvial deposits in the Malacacheta region. The alluvial deposits consist of resedimented gravel along the present drainage streams. The paleo-alluvial deposits are richer in alexandrite, and show well-developed soil horizons covering the alexandrite-bearing gravel layer. Alexandrite grains show angular shapes with very sharp edges, suggesting transport for short distances. The country rocks are quartz-mica schist and peraluminous mica schist (Salinas Formation), covered by alternating mica schist and quartzite layers (Capelinha Formation). Both formations are of Neoproterozoic age. They host tectonic slabs of metaultramafic rocks, and are cut by intrusive granites of Cambrian age. No alexandrite-bearing rock has been found in the area, probably due to the intense tropical weathering. However, some of the mapped rocks are sources for Be (granites), Cr (metaultramafics) and Al (peraluminous schists), the essential elements for alexandrite crystallization. We suggest a metasomatic system of Cambrian age for alexandrite genesis in the area, involving the interaction of granite-related Be-rich fluids with metaultramafic rocks and peraluminous schists.
ISSN: 0104-4486
metadata.dc.rights.license: Os direitos autorais dos trabalhos publicados na Geonomos são do autor, com direitos de primeira publicação para a revista. Fonte: Geonomos <>. Acesso em: 24 set. 2019.
Appears in Collections:DEGEO - Artigos publicados em periódicos

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