Why did the British call India the jewel in the crown?

The phrase is attributed to Benjamin Disraeli, the British prime minister from 1874 to 1881. His policies spurred the expansion of the British Empire, in which he called India "the brightest jewel in the crown". In 1876, Queen Victoria was proclaimed Empress of India, and British monarchs retained the title until 1947.

India had valuable resources that Europe wanted to exploit, like mineral ores and textiles. Even more importantly, it was both a huge source of cheap labor and a large market for British goods. As its largest colonial territory, India was the most important of the overseas possessions of the British Empire.

India was the centerpiece, the "Jewel in the Crown" of the empire. Trade with and eventual political dominance over India was what provided Britain with large parts of it's wealth in the 1700-1900's. India provided huge resources and massive markets for British factories and goods. It provided tax income, natural mineral wealth, and a population who were inducted into the British armies and civil services. Indian Clerks and Soldiers worked and fought around the Empire.

Much of the early Empire was built around India, areas conquered or "influenced" in order to provide routes to India, or protection for India. A framework like the metalwork around a diamond in a crown.

The central diamond in the British State Crown is called the "Heart of India" and is one of the largest diamonds in the world, if not the largest.
India was the jewel in the British Empire because at that time India was rich in spices, silk, indigo, gold, cotton and other products. India was both prosperous and rich. Traders who came to India gained riches. At that time pepper which was very famous and valuable in India was known as the black gold in the British empire.