optical flint

British  

noun

1. Also called: flint glass.  an optical glass of high dispersion and high refractive index containing lead oxide. They are used in the manufacture of lenses, artificial gems, and cut glass

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Example Sentences

While Dollond's invention was of immense value, it remained that flint object glasses larger than two and one-half inches in diameter could not, for some years, be manufactured, but about the opening of the nineteenth century, Guinand, a Swiss, discovered a process of making masses of optical flint glass sufficiently large as to admit of the construction from them of excellent lenses of sizes gradually increasing as time and experimenting went on.

From Project Gutenberg