INGENUITY AND LUXURY 



metal, copper, lead, tin, pewter, felt, or one of half 

 a dozen other materials that have been found to be the 

 best for polishing the particular stone in hand. It 

 is smeared with some such material as rotten-stone. 



Cutting reduces the weight of the rough stone very 

 materially, as is shown by the following table giving 

 the loss in weight of some of the famous diamonds: 



Name Original Weight Weight after Cutting 



Carats Carats 



Excelsior 970 239 



Great Mogul 560 279 



Orloff 400 193 



Koh-i-noor 393 186 



Star of the South 250 125 



The original weight of some of these gems can only 

 be estimated. The carat is the unit of weight for 

 precious stones, and is about 3.2 grains. 



DIAMONDS IN THE ROUGH 



Diamonds crystallize in the cubic system and gen- 

 erally occur in the octahedron, or rhombic dodecahe- 

 dron form. Sometimes they have the appearance of 

 being spherical, and frequently they are twinned. 



At the present time the South African mines are the 

 world's chief source of diamonds. The diamond- 

 bearing material of these mines is found in fissures in 

 the rocks supposed to be of volcanic origin, which have 

 been filled in with the material containing the diamonds 

 at a later period. This diamond-bearing earth is 

 called "Kimberlite," and occurs in three distinct 

 layers with three degrees of hardness. The lowest of 

 these is known as "hard bank," which, as its name indi- 



