Fig. 1

Ancient alkali glass. Essential components totalling to 85–95 wt%. Analyses from Bezborodov (1975), Brill (1999), Geilmann and Jenemann (1953), Geilmann (1955) and Wedepohl (1993, 1998, 2003). Inserted melting diagrams after Morey et al. (1930) and Shahid and Glasser (1971). a K–Ca glass red circles, N = 760. Analyses from Barrera and Velde (1989), Maus and Jenisch (1999) and Gerber and Stern (2012). b Na–Ca glass blue circles, N = 560. Analyses from Arletti et al. (2010), Foster and Jackson (2009, 2010), Verità (1985, 1995) and Wolf et al. (2005)