Flint Glass or Optical instrument Glass

Flint Glass:- Flint glass also known as Optioical instrument glass.

Flint glass is formed when potassium and lead silicate are heated at appropriate temperature.

K₂Co₃+ PbCo₃ +SiO₂  ------>  Flint Glass

Flint glass has high reflective index that is why it is used to make optical instrument like Prism, Lense etc.