Glass containing lead oxide, used for its high refractive index (often in cut glass) or for its ability to block ionizing radiation.

objective (part of a microscope, telescope, etc.)

A variety of hard glass of fine quality, made in Bohemia. It is of variable composition, containing usually silica, lime, and potash, rarely soda, but no lead. It is often remarkable for beauty of colour.

(archaic) A mirror.

The mineral galena.

Sheet glass made by blowing the glass in the form of a cylinder which is then split longitudinally, opened out, and flattened.

An early type of window glass made by blowing glass into a hollow globe (crown) and then flattening it on a punty, reheating and spinning out into a flat disk by centrifugal force.

A heavy optical glass, consisting essentially of potassium borosilicate.

The fused material for making glass.

A silicate of sodium or potassium, found commercially as a white, glassy mass, a stony powder, or dissolved as a viscous, syrupy liquid; used for making fabrics fireproof, for hardening artificial stone, etc.