Final answer:
Marble is the impure masses that make up limestone. It is formed through heat and pressure and has colorful markings due to impurities in the limestone. It has been used in buildings and sculptures for centuries.
Step-by-step explanation:
The rock 'limestone' consists of impure masses of marble. Marble is formed when limestone is changed by heat and pressure and recrystallizes into a light-colored rock. Impurities in the limestone cause the colorful markings in marble. It is found in extensive deposits and has been used in buildings and sculptures for hundreds of years.