PRECIOUS STOXES, OPALS, ETC. 45 



Obsidian. — The most important article obtained from the earth, to the Aztec, 

 was obsidian, a volcanic glass, called by them Itzi/i, a knife, or shining stone. 

 Ancient mines of it are found to-day in many localities, particularly in the Cerro 

 de las Navajas, near Pachuca, about which are scattered, it is said, hundreds of 

 tons of fragments. Everywhere, over plain and valley, may be encountered knives, 

 arrow and spear points, of obsidian, showing how numerous were the uses to 

 which it was put during the time of the early people of Mexico. 



Porphyry. — Chihuahua: Hidalgo, Jalisco, Puebla, Queretaro, and Zacatecas. 



Potter's Clay. — In Guanajuato; and Leon of the same State. 



Salt Districts. — Lower California, Colima, Jalisco, Michoacan; San Luis, 

 Potosi ; Tequesquites, Tamaulipas ; Valle\' of Mexico ; Yucatan and Zacoalco. 



Tequesquite. — The surface exposed by the subsidence of Lake Tezcoco is 

 sterile, treeless, almost herbless, but a few inches above that of the lake itself. 

 Only a few plants appear upon it, belonging to the genera of Gratiola, Atriplex, 

 etc.; such, in short, as thrive in a soil highly impregnated with saline substances. 



" The landscape," says a very intelligent writer, " is that of -a dreary desert, in 

 places resembling the African Sahara; but in other places more like a northern 

 moorland, with a hoar-frost, or a slight sprinkling of snow upon the ground ; for 

 here the tequesquite appears, coating the surface, sometimes of a snow-white color, 

 sometimes with a yellowish tinge. It is the natron, a mixture of carbonate and 

 sulphate of soda. The poor people dwelling around the lake collect and bring it 

 to market; and it is employed in various waj-s, — for washing, for the fabrication 

 of soap, and also in the cooking of one of the most common of Mexican dishes, 

 the frijoles. They also manufacture a coarse kind of salt out of the earth thus 

 impregnated, by a rough process known to them in the days of Montezuma. It 

 seems to ooze out of the eai-th, fonning an efflorescence on the surface, sometimes 

 td the extent of a uniform stratum of an inch or so in thickness." 



There is a very extensive deposit of this mineral salt in the State of Zacatecas, 

 from which the miners of that section draw large quantities for use in smelting. 

 This saline incrustation is formed on the surface of a shallow lake, which in a 

 good year was estimated to yield 30.000 fatiegas, or 360,000 arrobas (twenty-five 

 pounds) yearly, and which was formerly worth one dollar the mule-load. The 

 deposition depends upon the season, being best and thickest with an average 

 rainfall. The only preparation it needs is to be gathered into conical, earth-covered 

 hillocks, whence it is taken away by the purchasers. 



Copperas. — In Tepeji, State of ^tlexico; I'arranca de Tollman, in Hidalgo; 

 Taretan and Huetamo, State of Michoacan. 



Coals, and Mineral Oils. — Anthracite: la Tequisquiapan, State of Quere- 

 taro, and Tecomatlan, Puebla. 



Pit- Coal. — In Tecomatlan, State of Puebla. 



Petroleum. — Puerto Angel, State of Oa.xaca. 



Naphtha. — In Guadalupe, Hidalgo, federal district. 



Stone Coal. — In Chamacuero, State of Guanajuato. 



For further details, see Resources of the various States, Industries, etc. 



