Glass 01

The major raw material
of glass is sand
(or "quartz sand")
that contains almost
100 % crystalline silica
in the form of quartz.
Although it is almost
pure quartz, it may
still contain a small
amount (less than 1 %)
of iron oxides that
would color the glass,
so this sand is usually
depleted before
production to reduce
the iron oxide amount
to less than 0.05 %.

For more information visit
wikipedia.org