You can find the mines for tanzanite (a blue-purple gemstone) only in tanzania, but they are owned by the local government. given that no one is allowed into the mines without government permission, the market structure for tanzanite highly resembles that of a monopoly. in an imaginary country, there is only one federally licensed lottery agency in any state; that is, it is impossible for any private firm to start up a competitive lottery without a government license to do so. in the electricity industry, low average total costs are obtained only through large-scale production. in other words, the initial cost of setting up all the necessary wiring makes it risky and, most likely, unprofitable for competitors to enter the market.