Abstract
Gem-quality elbaite from Paraíba, Brazil, containing up to 1.4 wt% Cu has been characterized using optical spectroscopy and crystal chemistry. The optical absorption spectra of Cu2+ in these tourmalines consist of two bands with maxima in the 695- to 940-nm region that are more intense in the E ⊥ c direction. The vivid yellowish green to blue-green colors of these elbaite samples arise primarily from Cu2+ and are modified to violet-blue and violet hues by increasing absorptions from Mn3+.
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