Tribes adapted to California's many climates. Coastal tribes were a major source of trading beads, which were produced from mussel shells and made using stone tools. Tribes in California's broad Central Valley and the surrounding foothills developed early agriculture, while tribes living in the mountains of the north and east relied heavily on salmon and game hunting, and collected and shaped obsidian for themselves and trade. The harsh deserts of the southeast were home to tribes who learned to thrive by making careful use of local plants and by living in oases or along water courses. Local trade between indigenous populations enabled them to acquire seasonings such as salt, or foodstuffs and other goods that might be rare in certain locales, such as flint or obsidian for making spear and arrow points.