Glass for data storage medium substrate, glass substrate for data storage medium, and magnetic disk

A glass comprising, in terms of mole percentage based on oxides:

• 60% or more of SiO2,
• more than 6.5% and less than 13% of Al2O3,
• 0 to 5% of MgO,
• 1 to 12% of CaO,
• 0 to 2% of SrO,
• 0 to 2% of BaO,
• 0 to 1% of TiO2,
• 0% or more and less than 4% of Li2O,
• 3 to 12% of Na2O,
• 0% or more and less than 4% of K2O, and
• 0% or more and less than 0.01% of B2O3,
• wherein:
• a total content (R2O) of Li2O, Na2O and K2O is 3 to 12%,
• a total content of SiO2 and Al2O3 is 80.5% or less,
• a molar ratio (SiO2/Al2O3) of the SiO2 content to the Al2O3 content is higher than 5,
• a molar ratio [(SiO2+Al2O3)/R2O] of a total content (SiO2+Al2O3) of SiO2 and Al2O3 to R2O is higher than 9, and
• contents of SiO2, Al2O3, RO and R2O are such that a value obtained by the Formula (1) is greater than 90:
• [SiO2]+2×[Al2O3]+0.8×[RO]−0.5×[R2O] Formula (1),
• wherein in the Formula (1), RO represents a total content of MgO, CaO, SrO, and BaO.

A glass comprising, in terms of mole percentage based on oxides,

• 60% or more of SiO2,
• 4% or more and less than 15% of Al2O3,
• 0 to 5% of MgO,
• 1 to 12% of CaO,
• 0 to 7% of SrO,
• 0 to 5% of BaO,
• 0 to 10% of TiO2,
• 0% or more and less than 4% of Li2O
• 0% or more and less than 4% of K2O,
• 3% to 12% of Na2O,
• 0% or more and less than 0.01% of B2O3 and
• 0 to 5% of ZrO2,
• wherein:
• a total content of SiO2 and Al2O3 is 80.5% or less,
• a molar ratio (MgO/RO) of MgO to a total content (RO) of MgO, CaO, SrO, and BaO is 0.7 or lower, and
• contents of SiO2, Al2O3, RO and R2O are such that a value obtained by the Formula (1) is 90 or more:
• [SiO2]+2×[Al2O3]+0.8×[RO]−0.5×[R2O] Formula (1),
• wherein in the Formula (1), RO represents a total content of MgO, CaO, SrO, and BaO, and R2O represents a total content of Li2O, Na2O and K2O.