Patent ID: 7071131

Claim:
A mineral glass having a composition, expressed in percentages by weight of oxides, which essentially consists of: SiO 2 65–70 Al 2 O 3 18–20.5 Li 2 O 2.5–3.8 MgO 0.55–1.5 ZnO 1.2–2.8 BaO 0–1.4 SrO 0–1.4 with BaO+SrO 0.4–1.4 with MgO+BaO+SrO 1.1–2.3 Na 2 O 0–<1 K 2 O 0–<1 with Na 2 O+K 2 O 0–<1 with 2.8 ⁢ ⁢ Li 2 ⁢ O + 1.2 ⁢ ⁢ ZnO 5.2 ⁢ ⁢ MgO > 1.8 TiO 2 1.8–3.5 ZrO 2 0.8–1.6 with 2.2 < TiO 2 ZrO 2 < 4.4 ; and, optionally, an effective, non-excess amount of at least one fining agent.