Garnets are found in the Sierra de Gata and in the Sierra Nevada fine marble is quarried.
For the next five years he sought every opportunity of inflicting defeat and humiliation on the Spanish navy, and he distinguished himself by his bravery in the engagement at Guetaria (1638), the expedition to Corunna (1639), and in battles at Tarragona (1641), Barcelona (1643), and the Cabo de Gata.
The principal right-hand tributaries, besides the Gallo and Zezere, are the Jarama, descending from the tableland of New Castile a little below Aranjuez, the Alberche and the Tietar, which collect their head waters from opposite sides of the Sierra de Gredos, and the Alagon, from the rough and broken country between the Sierras de Gredos and Gata.
On the west another rough and hilly tract, similar to that which divides it from the Sierra de Guadarrama in the east, separates it from the Sierra de Gata, the westernmost and the lowest of the Spanish sierras belonging to the series.
The Sierra de Gredos has a road across it connecting Avila with Talavera de Ia Reina by the Puerto del Pico; but for the most part there are only bridle-paths across the Gredos and Gata ranges, and no railway crosses either of them, although the line from Plasencia to Salamanca skirts the Sierra de Gredos on the west.