The present invention relates to: novel glass-ceramics of .beta.-quartz and/or of .beta.-spodumene; articles made from said novel glass-ceramics; and ithium alumino-silicate glasses, which are precursors of said novel glass-ceramics; methods of preparing said novel glass-ceramics and articles made from said novel glass-ceramics. The present invention relates to the use of SnO.sub.2 and of Br, as an agent for fining the glass-ceramic glass precursor.