Black tea is the most well-known variety of tea in the West. Known as "red tea" in China, black tea leaves are fully oxidized. In the case of most black teas, younger leaves are picked before being withered, rolled, fully oxidized, and fired. While created originally in China, black teas are now cultivated worldwide. Some of the most famous black teas come from the Indian regions of Assam, Darjeeling, and Nilgiri as well as Sri Lanka. The use of machines is becoming more common, but the best black teas are those entirely done by hand. Machine-processed teas tend to be of lower quality and are generally used in tea bags.per-tea research shows that most of the tea bags are made of the remaining tea or poor quality tea.