No matter what the medicine-man may lack, he will, if it be possible, provide himself with some of the impure malachite known to the whites of the Southwest as turquoise. In the malachite veins the latter stone is sometimes found and is often of good quality, but the difference between the two is apparent upon the slightest examination. The color of the malachite is a pea green, that of the turquoise a pale sky blue. The chemical composition of the former is a carbonate of copper, mixed with earthy impurities; that of the latter, a phosphate of alumina, colored with the oxide of copper. The use of this malachite was widespread. Under the name of chalchihuitl or chalchihuite, it appears with frequency in the old Spanish writings, as we shall presently see, and was in all places and by all tribes possessing it revered in much the same manner as by the Apache. The Apache call it duklij, "blue (or green) stone," these two colors not being differentiated in their language. A small bead of this mineral affixed to a gun or bow made the weapon shoot accurately. It had also some relation to the bringing of rain, and could be found by the man who would go to the end of a rainbow, after a storm, and hunt diligently in the damp earth. It was the Apache medicine-man's badge of office, his medical diploma, so to speak, and without it he could not in olden times exercise his medical functions. [Illustration: Front view. Rear view. FIG. 445.--Tzi-daltai amulet (Apache).] In the curious commerce of the Indian tribes, some possessed articles of greater worth than those belonging to their neighbors. In the southwest the red paint sold by the tribes living in the Grand Canyon of the Colorado was held in higher repute than any other, and the green stone to be purchased from the Rio Grande Pueblos always was in great demand, as it is to this day. Vetancurt[723] speaks of the Apache, between the years 1630 and 1680, coming to the pueblo of Pecos to trade for "chalchihuites." John de Laet speaks of "petites pierres verdes" worn in the lower lip by the Brazilians.[724] Among the Mexicans the chalchihuitl seems to have been the distinguishing mark or badge of the priesthood. Duran, in speaking of the consecration of a sacrificial stone in Mexico by Montezuma the elder, and his assistant or coadjutor, Tlacaclel, says: "Echáronse á las espaldas unas olletas [I do not know what this word means] hechas de piedras verdes muy ricas, donde significaban que no solamente eran Reyes, pero juntamente Sacerdotes."[725] [Illustration: FIG. 446.--Tzi-daltai amulet (Apache).] Among the tribes in Central America, a chalchihuitl was placed in the mouths of the dying to receive their souls: "que era para que recibiese su ánima."[726]