448 SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



obsidian, and sink in liquid No. 4 (sp. gr. = 2'65), in which obsidian floats. Black haematite 

 is not infrequently used as a ring-stone, but its lustre is more distinctly metallic, and on 

 unglazed porcelain it gives a red streak, while that of obsidian is colourless. 



Obsidian of various kinds is widely distributed. It is found in some districts in 

 extensive rock-masses built up of irregular, angular, or rounded blocks. A comparatively 

 large proportion of these rock-masses is sufficiently pure and homogeneous to be cut for 

 ornamental purposes. The rough material being thus very abundant, it is not surprising 

 to find that the price of a cut stone is very little in excess of the sum paid for the labom* 

 of cutting. 



The distribution of obsidian is so general that it would be impossible to mention all 

 the localities for this rock by name ; a few only of the most important will now be dealt 

 with. 



In Europe the island of Lipari is a locality at which fine obsidian occurs in abundance. 

 A lava stream of obsidian, ranging in thickness up to 100 feet and having a breadth 

 of an eighth of a mile, stretches from Monte Campo Bianco to the sea at Capo Castagno. 

 The material also occurs in great abundance in the neighbouring island of Vulcano. On 

 the island of Ponza there are dykes of black obsidian penetrating the volcanic tuffs. It is 

 abundant in Hungary ; and in Iceland there is so much fine material suitable for cutting 

 that obsidian is often referred to by lapidaries as " Icelandic agate."' 



The country in which in former times obsidian was most extensively used for all 

 purposes is Mexico. Arrow-heads, spear-heads, knives, and other tools and weapons were 

 fashioned out of obsidian by the ancient Mexicans, and, indeed, by some of the native 

 Indians at the present day. They had learned the art of striking off a long, thin splinter 

 of obsidian, with an edge so fine and sharp that it could be used as a knife, or even as a 

 razor. Discoveries in the dwelling- and burial-places of these ancient people have shown 

 that obsidian was fashioned into mirrors, masks, and all kinds of personal ornaments. The 

 distribution of the mineral is general throughout Mexico, and extends northwards and 

 southwards beyond the borders of that coimtry. The ancient Mexicans appear to have 

 derived most of their rough material from one particular spot, the so-called Cerro de las 

 Navajas (Hill of Knives), first exactly described by Alexander von Humboldt. It is 

 situated near Real del Monte, in the State of Hidalgo, north of the city of Mexico and near 

 the town of Atotonilco. The ancient mines, which were worked long before the conquest 

 of Mexico by the Spaniards, are still to be seen here, the marks of an ancient civilisation. 

 The material found here shows a variety of colours, and specimens with a very fine sheen are 

 met with, but the greater part of it is the ordinary black variety. 



Among the localities in the United States at which fine obsidian occurs, may be 

 mentioned Silver Peak, in bhe State of Nevada, and Obsidian Cliff, in the Yellowstone 

 National Park. The brown and grey streaked " mountain mahogany " is found, together 

 with other kinds of obsidian, along the Pitt river in California, and there are many other 

 localities in this country which yield material suitable for cutting. 



A locality of some importance in Asia is the Caucasus. Among the obsidian which is 

 mined here is some of the variety which exhibits a coloured sheen. The material found at 

 Mount Ararat has a very rich sheen, and is worked at Tiflis into personal ornaments, vases, 

 bowls, and other large objects. The balls of obsidian found in the Marekanka river at 

 Okhotsk in eastern Siberia are known to petrologists as marekanite, and are sometimes 

 utilised for various ornamental purposes. Each ball may be uniformly coloured brown, 

 grey, yellow, or red, or it may exhibit a number of colours. Similar material is found at 

 other places, for example, in Mexico. 



