Kalkutta was an important trading center for diamonds in central India. Diamonds were traded to the east and west of India and were recognized by various cultures for their gemmological or industrial uses. In his work "Naturalis Historia", the Roman writer Pliny the Elder noted diamond's ornamental uses, as well as its usefulness to engravers because of its hardness. It is however highly doubtful that Pliny meant diamonds, and it is assumed that in fact several minerals such as corundum, spinel, or even a mixture with magnetite were all referred to by the word "adamas". Diamonds eventually spread throughout the world, even though India had remained the only major source of the gemstone until diamonds were discovered in Brazil in 1725. A Chinese work from the 3rd century BC mentions: "Foreigners wear it [diamond] in the belief that it can ward off evil influences". The Chinese, who did not find diamonds in their country, initially did not use diamond as a jewel but used it as a "jade cutting knife". Diamonds reached ancient Rome from India. Diamonds were also discovered in 700 in Borneo, and were used by the traders of southeast Asia. The modern era of diamond mining began in the 1860s in Kimberley, South Africa with the opening of the first large-scale diamond mine. The first diamond there was found in 1866 on the banks of the Orange River and became known as the Eureka Diamond. In 1869, an even larger diamond was found on the slopes of Colesberg Kopje on the farm Vooruitzigt belonging to the De Beers brothers. This sparked off the famous "New Rush" and within a month, 800 claims were cut into the hillock which were worked frenetically by two to three thousand men. As the land was lowered so the hillock became a mine—in time, the world-renowned Kimberley Mine. Following agreement by the British government on compensation to the Orange Free State for its competing land claims, Griqualand West was annexed to the Cape Colony in 1877. From 1871 to 1914, 50,000 miners dug the Big Hole with picks and shovels, yielding of diamonds, and by 1873 Kimberley was the second largest town in South Africa, having an approximate population of 40,000. The various smaller mining companies were amalgamated by British imperialist Cecil Rhodes and Charles Rudd into De Beers, and The Kimberley under Barney Barnato. In 1888, the two companies merged to form De Beers Consolidated Mines, which once had a monopoly over the world's diamond market.