noun
flint glass
A type of optical glass with high refractive index and dispersion, used in lenses and prisms.
このレンズにはフリントガラスが使われている。
Flint glass is used in this lens.
Variant with interpunct; less common but still encountered.
Kanji spelling using 硝子 for glass; rarely used in modern texts.
Crown glass is another type of optical glass with lower refractive index and dispersion, often paired with flint glass in achromatic lenses.
From English 'flint glass', referring to the original use of flint as a source of silica.