The correct answer is gypsum.
Key Points
- Glass is formed when molten material is cooled so quickly that its constituent atoms do not have time to align themselves into an ordered lattice.
- Soda ash varies in density, size, and shape when mined and processed.
- This flexibility allows it to be used in a variety of everyday products like glass.
- Specifically, soda ash is used to make the most common type of glass, soda-lime silica glass.
- It is used as the main ingredient because soda ash naturally reduces melting temperatures and its alkali effectively supports the shaping of the glass item.
- Alumina is used in glassmaking because of its superior mechanical and optical properties.
- Alumina can form glass if it is alloyed with calcium or rare-earth oxides.
- But the required quenching rate can be as high as 1000 degrees per second, which makes it difficult to produce bulk quantities.
- Glass manufacturers add borax to the silica base to:
- significantly lower melting temperature and viscosity, inhibit crystallization of the glass, control thermal expansion, and inhibit devitrification.
- The resulting products have inherent durability and chemical resistance and are tough enough to withstand considerable mechanical or thermal shock.