Silicon Dioxide
The key element in cement and glass is silicon.
Pyrex is also known as borosilicate glass. It consists primarily of Silica and boron oxide. According to Wikipedia, typical borosilicate glass is composed of: 70% silica (silicone dioxide SiO2), 10%...
metallic oxides such as those of copper, cobalt, etc are used to color glass.
Tellurium