232 SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



site, tourmaline, epidote, felspar (oligoclase), and, lastly, the rarest constituent, diamond. 

 The diamonds occur as small, angular, rarely water-wom, water-clear grains or broken 

 fragments. These rarely exceed 0"25 mm. in diameter, though one crystal has been found 

 measuring 15 mm. across. The transparency of the stones is greatly impaired by the 

 presence of numerous enclosures, some being cavities containing gas, while others are micro- 

 scopic crystals of an unknown substance. That these small grains are indubitable diamonds 

 is demonstrated both by their hardness and by the fact that they are combustible in oxygen, 

 the products of combustion being pure carbon dioxide. 



The minerals associated with the diamond in Lapland are practically the same 

 as in India and Brazil ; epidote, however, while present in India is absent in Brazil, 

 and the hydrous chloro-phosphates, so abundant in Brazil, are here absent. Velain 

 has expressed the opinion that the diamond here originated in the pegmatite ; the 

 mother-rock and the precious stone having been formed concurrently, as is also supposed by 

 Chaper to be the case with the pegmatite at Wajra Karur, near Bellary in southern India, 

 described above. In any case the Lapland diamonds must have been derived from one 

 of the ancient crystalline rocks mentioned above, since no other type of rock is present in 

 the whole of this region. No recent accounts of this locality have been published, and 

 further investigation is much to be desired, since it would probably shed fresh light on the 

 problem as to the nature of the original mother-rock of the diamond, and on the doubtful 

 occurrence of diamond in pegmatite at Wajra Karur. Though of no commercial or 

 economic importance, the discovery of Rabot and Velain is of great scientific interest and 

 should be aJssiduously followed up. 



10. DIAMONDS IN METEORITES. 



In recent years our knowledge of the distribution of diamonds has been extended in an 

 interesting direction by the observation that this mineral occurs in a number of meteorites 

 in the form of small, usually microscopic, grains of a grey or black colour, closely resembling 

 carbonado. Diamond is thus a substance which is not confined to the earth, but is present 

 in extra-terrestrial bodies, fragments of which, from time to time, fall upon the earth's 

 surface. From an aesthetic point of view, meteoric diamonds are, of course, valueless ; their 

 interest and importance in connection with the natural history of the mineral is, on the 

 contrary, very considerable, and it is fitting that this particular occurrence of the diamond 

 should receive appropriate mention, especially as on it various theories as to the mode of 

 origin of the diamond in the earth''s crust have been based. 



The meteorite which fell in Russia on the morning of September 22, 1886, in a field 

 three miles from the village of Novo-Urei, on the right bank of the Alatyr, a river in the 

 Krasnoslobodsk district of the government of Penza, was the first m which diamonds were 

 observed. It was examined by Messrs. Jerofejeft" and Latshinoff", and was found to consist 

 of the minerals olivine and augite, with interspersed carbonaceous matter and metallic 

 nickeliferous iron. The carbonaceous substance contained small greyish grains, the 

 hardness, specific gravity, chemical composition, and appearance under the microscope of 

 which, proved them to be undoubtedly diamond (carbonado). The results arrived at by 

 these investigators have been fully confirmed by others. In this stone diamond was present 

 in the proportion of 1 per cent., so that, since the whole meteorite weighed 1762'3 grams 

 (rather less than 41bs.), the total amount of diamond present was 17*62 grams or 85'43 

 carats. 



Black grains of diamond have also been observed in the meteoric stone of Carcote, in the 

 desert of Atacama, in Chile. Diamonds have subsequently been found, usually in meteoric 



