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ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 64 



HARDNESS OF THE DIAMOND 



KNOOP INDENTER 

 8000 — 



HARDNESS 

 Kg/mm^ 



4 5 6 



IliML Moh HARDNESS 



Figure 2. — Diamond is main' times harder tliaii ruby and sapphire. 



more severe than in engagement ring service. A suitable diamond saw 

 can be used to cut concrete, for example, which it does, much as a steel 

 saw cuts wood. Even more important, diamond wheels are used to cut 

 the hardest and strongest metals and alloys — like Carboloy cemented 

 carbides — and the vital industrial usefulness of these carbides depends 

 upon the availability of diamond for cutting these materials during 

 manufacture. 



Fortunately, diamonds do not have to be beautiful in order to be 

 hard. The bulk of the diamonds dug from the earth are small, dis- 

 colored, and not worth polishing, but their hardness is the same as 

 diamond of gem quality. These poor cousins of the million-dollars- 

 an-ounce gem stones are worth only a fraction of gem prices, which 

 fraction, however, is still about $6,000 a pound based on a typical dia- 

 mond grit price of $2.05 per carat. 



Soon after the discovery of the laboratory diamond process, we had 

 to face the question : "Can Man-Made diamonds be produced that are 

 good enough and inexpensive enough to compete with natural diamond 

 bort?" 



The answer came in a remarkably short time. A team of scientists, 

 engineers, and manufacturing experts joined forces to make these Man- 

 Made diamonds a competitive industrial product, and — as plate 2, fig. 2, 

 shows — this objective was achieved in less than 3 years. 



