a4 
154 
The present specimen is rendered handsome, and serves two 
purposes here,-by giving an example of yellow fluor. 
There are also some varieties of octaédral Pyrites, a few little 
spots of Galena, &c. The whole stand on a piece of shat- 
tered schistose Limestone. 
TAB. CCLXXVI. 
Carbonate of Lime. 
Tuts singular modification of Carbonate of Lime came 
from the neighbourhood of the Ecton-mine, Staffordshire, 
having been gathered by W. E. Sheffield, Esq., who was 
so good as to favour me with the use of the specimen. The 
depth of two of the facets of each pyramid, or the want of 
a proper supply to give them a proportion to the others, is 
a sort of deception, as they are nearly the same with the 
foregoing, except one or two additional facets, and the dia- 
gonal mackling. Thus the wholeis shortly accounted for; 
and as these are extremely rare specimens, I was glad of an 
opportunity to show them, and to explain so instructive a 
lesson in Crystallography. 
The gangue is chiefly of variegated Pyrites, but in another 
specimen possessed by my friend there is much Sulphate of 
Barytes with the faces as in the geometrical figure at the 
bottom of tal. 72, giving them a singular sharp-edged ap- 
pearance; and the modifications of the Carbonate of Lime 
are rather more mixed, or have the other ends of the crystals 
appearing in some parts beyond the mackling, rather irre- 
cularly. Iam the more gratified in having the use of these 
specimens, as the mackle in such a direction in Carbonate of 
Lime has not, to my knowledge, been noticed before, nor 
is it mentioned by Haiiy, being in itself very puzzling. 
The place of intersection is parallel to one of the faces 
of the equiaxe rhomb, or to the edge of the nucleus, and 
corresponds with the diagonal fractures that may be obtained 
from some yarieties of Carbonate of Lime. 
