I S 2 5 3 
XIV. Observations on a new Species of hard Carbonate of Lime ; 
also on a new Species of Oxide of Iron . By the Count de 
Bournon, F. R. S. and L . S. 
Read May 2 6, 1803. 
CARBONATE OF LIME. 
A particular investigation which I undertook to make, of 
the immense variety of forms presented to us by the carbonate 
of lime, (many of which have never yet been described,) having 
led me to observe more accurately some specimens I had before 
examined, my attention was forcibly attracted by a group of 
hexaedral pyramidal crystals, which are in Mr. Greville’s 
noble collection. As the exterior appearance of these crystals 
was different from that which is peculiar to carbonate of lime, 
I was desirous to ascertain their nature, and therefore endea- 
voured to bring them, by splitting, into the primitive rhom- 
boidal form of this substance ; but, upon making the attempt, I 
perceived, to my great astonishment, not only that I was not 
able to obtain any fracture that could possibly belong to the 
planes of the primitive rhomboid, but also, that the substance 
strongly resisted every attempt I made to procure a fracture in 
any other direction. In fact, every fracture I could obtain was 
irregular, and possessed more or less of that vitreous appearance 
which is peculiar to the greater number of hard stones. So 
remarkable was the hardness of this substance, that, although 
the points of the crystals were very thin, and consequently might 
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