| abstract |
A crystal glass composition contains a main component comprising SiO 2, MgO and Al 2 O 3 and contains 2 to 20 parts by weight of B 2 O 3 based on 100 parts by weight of the main component. In the ternary diagram according to FIG. 1, the weight ratio (SiO 2, MgO, Al 2 O 3) lies in one of point A (44.0, 55.0, 1.0), point B (34.5, 64, 5, 1.0), point C (35.0, 30.0, 35.0) and point D (44.5, 30.0, 25.5,) enclosed area. |