DIAMOND. 
381 
thing but modified charcoal, and that, far from 
being indestructible, it may be entirely consumed 
by fire. Such, however, is the fact ; for the know- 
ledge of which we are particularly indebted to the 
decisive experiment of Mr. Tennant, though other 
chemists have not been deficient in their operations 
on the same subject. It was found from some ex- 
periments which preceded those of Mr. .Tennant, 
that the diamond, though it was capable of resist- 
ing the effects of violent heat in a close vessel, 
might be consumed when exposed to the joint 
action of heat and air. These experiments, how- 
ever, if we except those by Lavoisier, only proved 
the inflammability of the diamond. Mr. Tennant, 
and, we ought to add, M. Guyton, went further, 
and not only proved its combustible nature, but 
likewise ascertained its component parts. Accord- 
ing, therefore, to the present arrangement of mi- 
nerals, this substance is placed among the com- 
bustible bodies : nevertheless, we have taken the 
liberty to leave it at the head of the precious stones, 
as a more natural, though less scientific situation 
than the other. 
Diamonds, when brought to Europe in their 
rouo-h state, are said to be either in the shape of 
roundish pebbles with shining surfaces, or in oc- 
taedral crystals ; but they are not entirely con- 
fined to this form, as they vary in several respects, 
and sometimes occur with twenty-four and even 
forty -eight sides. 
