Flint glass is opticalglass that has relatively highrefractive index and lowAbbe number (highdispersion). Flint glasses are arbitrarily defined as having an Abbe number of 50 to 55 or less. The currently known flint glasses have refractive indices ranging between 1.45 and 2.00.

Traditionally, flint glasses werelead glasses containing around 4–60%lead(II) oxide; however, the manufacture and disposal of these glasses were sources ofpollution.

In many modern flint glasses, lead oxides are replaced with other metal oxides such astitanium dioxide andzirconium dioxide without significantly altering the optical properties of the glass.

Aconcave lens of flint glass is commonly combined with aconvex lens ofcrown glass to produce anachromatic doublet lens because of their compensatingoptical properties, which reduceschromatic aberration (colour defects).

With respect to glass, the termflint derives from theflint nodules found in the chalk deposits of southeast England that were used as a source of high purity silica byGeorge Ravenscroft,c. 1662, to produce apotashlead glass that was the precursor to Englishlead crystal.

• Crown glass (optics)
• Chromatic aberration
• Cup plate

• Kurkjian, Charles R.; Prindle, William R. (1998). "Perspectives on the History of Glass Composition".Journal of the American Ceramic Society.81 (4):795–813.doi:10.1111/j.1151-2916.1998.tb02415.x.