256 SCIENCE PROGRESS. 



A recent achievement in this direction has been the 

 manufacture of crystalline sapphire and ruby, by Haute- 

 feuille, Fremy and Verneuil (14). 



Finally we may notice some recent work which illus- 

 trates both the value and the need of experiment in con- 

 nection with the eenesis of certain minerals which are 

 found associated with basic rocks ; that is to say with 

 igneous rocks containing- less than 55 per cent, of silica. 



Among those minerals whose origin is shrouded in the 

 greatest mystery are platinum and diamond, which, like 

 several of the gems, are for the most part found in gravels 

 and river washings, and not in the original matrix. 



Some quite recent observations have contributed much 

 to a better understanding of their origin. 



In the first place Inostranzeff has found platinum 

 actually disseminated through a rock consisting mainly of 

 chromite and serpentine (15), that is to say an altered 

 basic rock of which the metal appears to have been origin- 

 ally a constituent ; with this discovery may be compared 

 that of a nickeliferous iron in serpentine from New Zea- 

 land ; this has been described by Ulrich under the name 

 Awaruite (16). 



Nickel-iron was formerly supposed to be exclusively 

 meteoric, but the large masses brought by Nordenskiold 

 from Ovifak in North Greenland have been proved to be 

 metallic concretions formed in basalt and not of meteoric 

 origin (17). 



Here then are three instances of metallic segregations 

 which have solidified from basic igneous rocks. 



Somewhat similar may be the history of the diamond ; 

 various occurrences of diamond in a natural matrix have 

 been reported, but they have always been somewhat 

 dubious ; only in the South African workings at Kimberley 

 is the occurrence of the gem difficult to explain on any 

 other hypothesis than that it has actually crystallised from 

 the serpentinous rock in which it is found. This, which is 

 a basic igneous rock known by the name of " blue ground," 

 fills vertical pipe-shaped shafts of unknown depth, and the 

 diamonds which are dispersed through it bear all the 



