Question #b7edc

1 Answer
May 16, 2017

Answer:

Because the sand is almost pure silicon dioxide #SiO_2#, or it is only mixed with colourless other compounds.

Explanation:

Sand is mostly #SiO_2#, but even small admixtures of other compounds may give a strong colour, e.g. iron silicates may give a red-brown colour.
Other silicates, like aluminium silicates, are also white.