ESSEX COUNTY. 
285 
The above remarks apply to the sand and gravel beds situated in the upper valleys of the 
Adirondack mountains, upon their less sloping sides, or where the inclination is only mode¬ 
rately steep. I find, however, in some of the deep depressions, where there are natural 
meadows, beds of clay, analogous to the porcelain clay from the ordinary varieties of granite. 
The hypersthene rock, like that of the granite of Johnsburgh, disintegrates, and finally de¬ 
composes ; the alkali leaving the alumine and silex of the feldspar, a complete separation of 
the elements ensues. The clay which results from this decomposition, collects slowly in those 
depressions which are favorably situated. These beds are found in the midst of the Adiron¬ 
dack mountains, where they are from eighteen hundred to two thousand feet above the level 
of Lake Champlain. No analysis has yet been made of this variety of cla}^ but probably 
the proportions of silex and alumine will not differ very materially from those of the common 
porcelain clays. From this clay an excellent brick has been made, which possesses very re¬ 
fractory powers: it at least has one property which is quite important, viz. that of remaining 
sound when dried in the sun or fire, and it may be heated suddenly without breaking or flying 
to pieces. The color is light blue, or bluish white ; but I have never observed it a pure white, 
neither does it become white by burning: the bricks are yellowish after burning. It is not 
so tenacious as the tertiary upon the lake, and does not adhere so obstinately to substances 
put into it; still it is ductile, and moulds well. I am inclined to believe that this clay is 
adapted to a variety of purposes; but as it has only been employed for brick, my belief is 
only a matter of opinion. Its fineness, and ability to stand high degrees of heat without melt¬ 
ing, but more than all its freedom from cracks when dried or burnt, impart a value to it above 
all ordinary clays. In the use of it for fire-brick, however, it is necessary that it should be 
employed with a pure siliceous sand. The sands and gravel in the immediate neighborhood 
being made up of a great amount of feldspar, operate as a flux to the clay, and will cause it 
to melt. It will be much better to employ it without sand, unless it be one composed purely 
of silex. 
Simple Minerals. 
The names of many of the simple substances have already been given; a brief repetition, 
however, is necessary in order to exhibit the mineral riches of this county in their true light. 
Those which occur in the condition of rocks, may be put first: 
1. Labradorite. This substance has not yet fallen under my notice under any form except the primary, 
and under cleavage planes. In this respect, it is analogous to the feldspar which forms the consti¬ 
tuent of ordinary granite. 
2. Calcareous spar, ox Carbonate of lime. Very few localities where it is crystallized. One of the 
most interesting varieties is the blue of Long pond. 
3. Magnetic oxide of iron. The same remark is called for in regard to its crj^stallization, as in the 
preceding substances. It is uncrystallized, except in the mass. Not a single crystal has fallen 
under my notice during the survey, though I have examined very carefully all the mines in the 
county. 
