2 
these shapes, mostly taking the form of Carbonate of 
Lime, and is often detected in the process shown in the 
upper figure. The upper surface is a smoothish Oxide of 
Zinc, and beneath still remains crystallized Carbonate of 
Lime. In the lower figure the Oxide of Zinc has sup- 
planted the Carbonate of Lime, and is cellular or porous, 
which is one of its characters, whence it is often called 
bony, from its resemblance to the cellular inner part of a 
bone. It is sometimes white, but mostly coloured by 
Oxide of Iron, with various ochrey tints, and seldom has 
any lustre. It is procured in large quantities for the ma- 
nufacture of brass, &c., and produces about thirty per 
cent of Zinc *. 
* Zinc has been found perfectly ductile if heated toa certain temperature. 
