Several rich silver mines were, in Spanish times, worked at Avo, at Cerillos, and in the Nambe mountains, but none are in operation at present. Copper is found in abundance throughout the country, but principally at Las Tijeras, Jemas, Abiquia, and Gudalupita de Mora, but until a recent period only one copper mine was wrought south of the placeres. Iron, though also existing in very large quantities, has been entirely overlooked. Coal is found in different localities—as in the Raton mountains; in the vicinity of the village of Jimez, south-west of Santa Fé; and in spots south of the placeres. Gypsum, common and selenite, are discovered abundantly, and it is said that most extensive layers exist in the mountains near Algodon, on the Rio Grande, and in the neighborhood of the celebrated Salinas. It is used as common lime for white-washing, while the crystalline or selenite is employed instead of window glass. About one hundred miles, south south-east of Santa Fé, on the high table land between the Rio Grande and Pecos, are some extensive salinas or salt lakes, from which all the salt used in New Mexico is procured. Large caravans from Santa Fé visit this place every year during the dry season, and return heavily laden with the precious deposits. They either sell it for one and sometimes two dollars per bushel, or exchange a bushel of salt for a bushel of Indian corn.
The climate of New Mexico differs of course in the higher mountainous parts from the lower valley of the Rio Grande; but, generally, it is temperate, constant and healthy. The summer heat in the valley of the river sometimes rises to near 100° Farenheit; yet the nights are always cool, pleasant, and refreshing. The winters are longer and severer than in Chihuahua, for the higher mountains are always covered with snow, while ice and snow are common in Santa Fé, though the Rio Grande is never sufficiently frozen to admit the passage of horses and vehicles. The sky is generally clear and the atmosphere dry. Between July and October rain falls; but the wet season is not so constant or regular as in the Southern States of the Mexican Republic. Disease seems to be very little known except in the form of inflammations and typhoidal fevers during the winter.