Diamantes de capa verde: freqüência, distribuição e possível origem nos depósitos diamantíferos

Diamantes de capa verde: freqüência, distribuição e possível origem nos depósitos diamantíferos de Minas Gerais.
Mottled green diamond crystals and green-coated diamonds are common in diamondiferous sedimentary deposits of Minas Gerais. Diamonds with this characteristic were studied in the most significant áreas of the Espinhaço Province and compared with diamonds of the Coromandel region. The frequency of green-coated diamonds in these deposits varies but is relatively high in the Espinhaço deposits with values of 25% or higher, locally up to 90%. On the other hand, in the Coromandel deposits this value is less than 0,5%. We discuss the two main hypotheses for the origin of the green coatings, i.e., radiation damage in situ, or the presence of chromophorous elements in the externai part of the crystals. Analitycal data reveal both factors contributed to the green color. However, the relative contribution of each to the intensity of green coloration has yet to be determined.