METALS, MINERALS, FOSSILS. ETC. 285 



skeletons. It has also been found covering one sacrificial altar, and regularly 

 disposed in the form of a crescent before another. (See pages 144 and 154.) 

 The suggestion has been advanced that it was consecrated to some divinity, 

 equivalent to the Mexican Tezcatlipoca, " Lord of the Light." 



The mica of the mounds is often found fissile and fragile, perhaps the result of 

 exposure to heat, but generally quite compact and possessing its original tenacity. 

 Some very fine specimens of the graphic or discolored mica have been found in 

 the mounds of the Scioto valley and elsewhere. Fifteen or twenty beautiful oval 

 plates of this variety were taken recently from a low mound near Lower Sandusky, 

 Ohio. They are beautiful specimens, stained with a solution of some of the oxides 

 of iron or manganese, during the process of crystallization. 



Mica, like many other substances, crystallizes in oblique rhombic prisms w^hose 

 planes are 60° and 120°. When these planes are colored, they resemble many 

 letters of the alphabet. The specimens in question are iridescent, exhibiting all 

 the prismatic colors when the light falls upon them in a certain direction. These 

 circumstances no doubt gave rise to the idea that they were painted hieroglyphics. 

 Graphic mica occurs, in place, on the Schuylkill, some distance above Philadelphia, 

 and probably in other localities. No original deposit of the mineral exists in the 

 State of Ohio. 



Obsidian, the itzli of the Mexicans, and gallinazo stone of the Peruvians. Fre- 

 quent reference has been had to this mineral, precluding the necessity of an extended 

 notice here. It has been observed in five of the mounds excavated in the Scioto 

 valley, from one of which a number of large and very fine specimens were obtained 

 (page 155). It is only found in the form of implements, such as knives and spear 

 and arrow-points. This mineral is a volcanic product, and occurs, so far as known, 

 no nearer than Mexico, where it is found in abundance. It is also found in Peru, 

 and was extensively used by the ancient inhabitants of both countries, for cuttino- 

 and warlike implements. They also, notwithstanding its obstinacy and fragility, 

 worked it elegantly into mirrors, ornamental rings, and masks.* Some specimens 

 have been discovered in the mounds of Tennessee, which were doubtless obtained 

 from the same source with those found on the Ohio.f All the specimens discovered 

 are glassy black, subtranslucent, and break with a clear conchoidal fracture. 

 According to Humboldt, the mountains of Jacul or Cerro Gordo, on the route 

 between Vera Cruz and the city of Mexico, furnished the celebrated itzli quarries 

 or mines of the ancient Mexicans ; the locality is still known as El Cerro de los 

 Nahijas, the Mountain of Knives.J This is believed to be the nearest point of its 



• * The Mexicans used blades of obsidian in the construction of their swords ; their sacrificial knives and 

 razors were of. the same material ; and, from practice, the}' became so perfect in their manufacture that, 

 according to Clavigero, "in the space of one hoUr, an artist could finish more than a hundred." — Clavi- 

 geio, vol. ii. p. 288. 



f Transactions of Ainericun EtIitioUKjical Suciety, vol. i. p. ytjl, 



J Researches, vol. ii. p. 204. 



