A glass ball with coloured glass shapes inside
Edo-Kiriko, a traditional cut glass craft in Asakusa,
Tokyo,
Japan. The glass has two layers, a coloured layer outside a clear layer.
Glass is a hard material that can be made in many shapes. It is usually transparent, but it can also be made in colours. Glass is mainly made of silica; glass made of silica only is called silica glass. It originated in India.
Glass used to make windows and bottles is a specific type called soda-lime glass, composed of about 75% silicon dioxide (SiO2), sodium oxide (Na2O) from sodium carbonate (Na2CO3), calcium oxide, also called lime (CaO), and several minor additives.