366 
STALACTITES. 
mines of iron, though, at the same time, it is com- 
posed entirely of carbonate of lime, except a very 
little oxide of iron with which the base of the 
branches is generally impregnated. 
The most, beautiful groups of this mineral are 
said to come from the mines in Syria, where the 
specimens have a silky or velvet-like surface, and 
are composed of converging needles. It is found 
likewise in several other places, but, for the most 
part, of an inferior colour. 
The other kind of incrustation which we meet 
with among the stalactites, is formed, like these 
bodies, of calcareous carbonate, but has obtained 
the name of altibaster. We are naturally led to 
suppose, from a proverbial expression, that ala - 
bastei • is a stone of transcendant whiteness ; never- 
theless, it is very rare to find it perfectly white, as 
it is generally veined or tinted with different shades 
of yellow, brown, or red. This assertion may ap- 
pear rather extraordinary to those who have been 
in the habit of seeing figures and ornaments of 
several kinds made of a beautifully white and trans- 
parent substance, under the name of alabaster. But 
this stone, which we so frequently meet with, is 
of a very different nature. It is formed of chalk 
combined with sulphuric acid, and known by the 
name of gypsum. This, when calcined, becomes 
the common plaster of paris. The true alabaster, 
on the contrary, is simple carbonate of lime, and of 
very different chemical properties from the other. 
This mineral is not confined to subterranean 
