We have developed the glass ceramics containing ruby crystals by heat treatment of a Cr3+-doped SiO(2)-Al(2)O(3)-Y(2)O(3) glass at 1550 degrees C. The shape of precipitated crystals in the glass matrix was rod type whose average width and length were around 10 and 200 mu m, respectively. From an X-ray diffraction measurement and an electron probe X-ray microanalysis, it was confirmed that the rod crystals were alpha-Al(2)O(3). Intense emission bands of Cr3+ at 694 nm, called the R-lines, were observed in the glass ceramics heat treated above 1300 degrees C. In addition, the intense red luminescence was observed only in the alpha-Al(2)O(3) rod crystals by a photoluminescence mapping image.