The invention relates to: a method of preparing glass-ceramics of .beta.-quartz and/or of .beta.-spodumene; a method of preparing articles made from said glass-ceramics; novel glass-ceramics of .beta.-quartz and/or of .beta.-spodumene; articles made from said novel glass-ceramics; and lithium aluminosilicate glasses, which are precursors of such novel glass-ceramics. The present invention relates to the use, as agent for fining the glass-ceramic glass precursor, of fluorine and at least one oxide of a multivalent element.