122 THE WEALTH OF THE SEA 



scratches do not show, because it is slightly translu- 

 cent. On account of its carbonate of lime content, 

 mineral acids attack it readily. Formerly it was 

 thought that the coral owed its color to its iron 

 content, but recently it has been shown that the 

 depth of color varies with the amount of organic 

 matter. Black coral and red coral, for instance, have 

 nearly the same composition, except that the former 

 contains about twice as much organic matter. Red 

 coral contains approximately 87 per cent of calcium 

 carbonate, 7 per cent of magnesium carbonate, 1.5 

 per cent of calcium sulphate, 1.5 per cent iron oxide, 

 1.5 per cent of organic matter, and 1 per cent of 

 silica and phosphoric acid. The silica, iron oxide, and 

 phosphoric acid do not exist in the coral as such, but 

 as no one knows just how they are combined they 

 are reported in the conventional way. 



The Fisheries 



Precious coral comes chiefly from the Mediter- 

 ranean and the Japanese seas. Some also is taken 

 from the Red Sea, but this is black in color, and is 

 not as valuable as the Mediterranean and Japanese 

 coral. 



Coral has been fished in many parts of the Med- 

 iterranean for many centuries. The most important 

 coral banks are those on the Algerian and Tunisian 

 coasts. Here the coral fisheries are carried on as 

 far as six or even eight miles from the shore and 

 at depths varying from ninety to nine hundred feet. 

 Important coral banks also lie on the coast of Sicily ; 

 the most productive is near Sciacca. These have been 



