As Sherlock suggests, the White Cliffs of Dover is made out of chalk.

The cliff.

Ummmm.Chalk. They do not need to see it on the white rocks to know it is helping their grip.

l thought chalk was used just to keep your palms, hands dry? No way that l rock climb, but l think that is the reason why.

Crampons and ice axes, maybe?

Do you think those cliffs were always white? No man. They used to be called the multicoloured cliffs of dover do not ya know.

it is called magnesium!