Which of the following statements are correct?
(i) Obsidian is the lightest rock in the world and is known as natural glass.
(ii) Shale is formed of clay particles that have been hardened together under high pressure.
(iii) Basalt is rich in minerals like iron and magnesium.
(iv) Bauxite is an ore of iron.
A(i) and (iv) only
B(ii) and (iv) only
C(ii) and (iii) only
D(i) and (iii) only