Assertion: tourmaline's source | /r/CapableOf | produce gem-quality tourmaline
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Source sentences:
text: Many sources have produced gem-quality tourmaline for the jewelry market, including the states of Maine (Simmons et al., 2005) and California (Fisher, 2011) in the U.S. as well as Brazil (Proctor, 1985a,b; Koivula and Kammerling, 1989), Madagascar (Dirlam et al., 2002), Afghanistan (Bowersox, 1985), Mozambique (Abduriyim and Kitawaki, 2005; Laurs et al., 2008), and Nigeria (Smith et al., 2001; Garba, 2003; Laurs, 2015; Olatunji and Jimoh, 2017).