Lisa Barkley, age 14, of Charlotte, North Carolina, for her question:

Is it true that mirrors are made from sand?

A smooth shiny mirror in no way resembles a handful of gritty sand. Nevertheless, sand is the main ingredient used to make the glass for the mirror. It has to be a special sand, rich in the mineral called silica. Silica alone can be melted to form crystal clear quartz material. But the high temperatures required make this too expensive for the glass used in mirrors.

Then limy calcium and a sodium compound are added to the silica sand, the mixture melts at 3000 degrees Fahrenheit. The molten material is refined through a series of treatments, cooled somewhat and treated some more to shape it into sheets of glass. To make a mirror, one side of a sheet of glass gets a very thin layer of metal plus several coats of other materials to protect it. But most of the mirror is glass. And sand accounts for more than 70 per cent of glass making ingredients.