When it’s used to refer to a material, the term glass can indicate any of a handful of compounds.
The most popular today is soda-lime glass, a variety made from silicate, lime and soda. It’s inexpensive to manufacture because all of its components are readily available in nature.
Other types of glass include fused quartz and borosilicate glass, known by the trade name Pyrex.
Crystal shares some properties in common with these types of glass, but it’s composition is unique too.
Most of the crystal shoppers today encounter is composed of silica, lead oxide, potash or soda, and a handful of other additives.
It’s the use of lead oxide that resulted in this material being called lead crystal. Truthfully, though, what most of us call crystal is rightfully lead glass.