Glass for magnetic recording medium substrate, magnetic recording medium substrate, magnetic recording medium, glass spacer for magnetic recording and reproducing apparatus, and magnetic recording and reproducing apparatus

A glass for a magnetic recording medium substrate or for a glass spacer for a magnetic recording and reproducing apparatus, which is an amorphous glass,

• wherein an SiO2 content is in a range of 56 mol % or more,
• an MgO content is in a range of 15 mol % or more and 28 mol % or less,
• an Li2O content is in a range of 0.2 mol % or more,
• an Na2O content is in a range of 5 mol % or less,
• a total content of Al2O3, MgO, and CaO (Al2O3+MgO+CaO) is 29.0 mol % or more and 36.50 mol % or less,
• the total content of SiO2, MgO, Li2O, Al2O3, and CaO (SiO2+MgO+Li2O+Al2O3+CaO) is 95.0 mol % or more,
• a mole ratio of the total content of SiO2 and MgO relative to the Li2O content [(SiO2+MgO)/Li2O] is 13 or more, and
• a mole ratio of a CaO content relative to a total content of Al2O3 and MgO [CaO/(Al2O3+MgO)] is 0.10 or less.