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done,) and attentively examining them, they 

 are found to have facets, though it is not 

 poffible to afcertain the number of them, as 

 piany of the angles have been defaced by 

 time. I Ihall only obferve, that having 

 broken one of thefe garnets into two 

 equal parts, the perimeter of each half 

 was o£tagonal. This fradture at the fame 

 time fhewed the texture of the garnet, 

 which is compofed of very thin circular 

 leaves. Thefe garnets are of different lizes, 

 from four lines and a half to one fixth of 

 a line. 



The furnace reduces the matrix-lava to a 

 compadl enamel of the colour of pitch ; 

 but it leaves the garnets untouched, which 

 only become fomewhat whiter, more vitre- 

 ous, and more hard. The blacknefs of the 

 enamel being a contrafh to the whitenefs of 

 the garnets, a great number of the latter be- 

 come confpicuous, which before were not 

 vifible in the lava; and, notwithftanding 

 their extreme minutenefs, they remain un- 

 injured by the fire. 



The 



