Why does iron, when added to quartz, cause the purple color of amethyst?
A) The presence of trace constituents can affect color.
B) Iron overpowers the silicon in quartz.
C) Amethyst is formed under extremely hot conditions.
D) Iron is red and silicon is blue, making purple.
Question 2
Why are diamonds so hard?
A) They are formed under very cold conditions.
B) They are held together by strong metallic bonds.
C) They are held together by strong ionic bonds.
D) They are held together by strong covalent bonds.