DIAMOND: OCCURRENCE IN NORTH AMERICA 227 



County ; this stone was not recognised as a diamond until 1883. It had been bought by 

 a Milwaukee clockmaker, who did not know what it was, for a dollar. A second still larger 

 stone, stated to have been found about the same time in the same district, was mislaid 

 before its real nature was known. In the year 1886 a pale yellow diamond, with the form 

 of an irregular rhombic dodecahedron, measuring 20 by 13 by 10 millimetres and weighing 

 21:^ carats, was found at Kohlsville in Washington County. Another stone of 6^ carats, 

 found at Saukville in Ozaukee County in 1880, was not determined to be diamond until 

 1896. Altogether, since 1883, seventeen diamonds, varying in weight from ^ to 2 1 J carats, 

 have been found in glacial moraines in the region of the Great Lakes of North America, 

 principally in the State of Wisconsin, but also in Michigan and Ohio. The predominating 

 crystalline forms are the rhombic dodecahedron and a hexakis-octahedron ; the stones are 

 colourless, or tinted with green or yellow. By plotting the diamond localities and the 

 directions of the glacial strias on a map. Professor W. H. Hobbs has recently (1899) shown 

 that the diamond probably came from somewhere near James Bay on Hudson Bay ; a more 

 detailed study of the glacial geology of the region will, however, be needed before the home 

 of the diamond can be exactly located. 



In the western region a certain number of diamonds have been met with in the States 

 of California and Oregon ; in the former the stones occur in gold-bearing detritus belonging 

 to two different periods of formation. Here, in Tertiary and even earlier times, the Sierra 

 Nevada and Cascade Range were drained by immense rivers, whose beds, which have been 

 traced for great distances, became filled with auriferous debris derived from these mountains. 

 Later on mighty volcanic eruptions took place, and the surface of northern California and of 

 Oregon was flooded with thick sheets of lava partly filling up the river valleys. The streams 

 and rivers of the present day, rising in the same mountains, cut out for themselves new 

 courses in these volcanic rocks, and have deposited in their beds auriferous debris derived 

 from the same mountains, and therefore of the same nature as the debris laid down in the 

 ancient river-beds. It was from these latter masses of debris that the enormous amount of 

 gold yielded by the Californian goldfields in the early days of their discovery, namely, about 

 the year 1848, was mainly derived. These later gold-sands are now exhausted, and mining 

 is at the present day confined to the earlier deposits of Tertiary and Pre-Tertiary alluvium, 

 which are overlain by lavas and which contain diamonds as well as gold. The pebbles and 

 diamonds of this alluvium are often cemented together by limonite to form a solid 

 conglomerate, which is very similar in appearance to the " tapanhoacanga ■" of the Brazilian 

 diamond-fields. 



The first find of diamonds took place in 1850 ; since then single stones, usually only of 

 small size, have been met with every year, the largest weighing 7^ carats. The diamonds 

 actually present pi'obably far exceed those actually found in number, for, during the process 

 of winning the precious metal, the solid, auriferous conglomerate is stamped to a fine 

 powder, and thus any diamonds present in it are also crushed and destroyed. As a matter 

 of fact, the presence of splinters of diamond in this crushed material has been frequently 

 observed. Moreover, it is possible that many stones have been lost on account of the 

 practice of ignorant miners, prevalent both here and in other countries, of testing the 

 genuineness of a supposed diamond by means of the hammer and anvil ; should such a stone 

 be genuine the test, owing to the brittleness and perfect cleavage of the diamond, results 

 in its complete fragmentation. 



The possible occurrence of diamonds in those parts of North America, for example 

 Indiana, which ai'e geologically very similar to other diamond-bearing districts, has often 

 been suggested. In many such places, however, the search has been unsuccessful, and stones 



