Porcelain is described as a white ceramic Ware that consists of quartz, kalin, and feldspar.

It is fired at high temperature on steel or cast iron to make the surface of some bathtubs, kitchen sinks and bathroom lavatories. Many times porcelain also refers to porcelain china which is a ceramic product with porcelain glaze. Fired porcelain is white, strong and hard. When sufficiently thin, it is also translucent

See also:
"Porcelain" is in the NAICS Code "327113"