ESSEX COUNTY. 
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17. Idocrase. This mineral occurs in very small crystals at Long pond. 
18. Sphene, has been observed at several localities, as Moriah, Long pond and Keene. 
19. Phosphate of lime, at Long pond. 
20. Proto-sulphate of iron, in Westport, and small crystals of the common variety are not uncommon. 
21. Graphite, usually disseminated in thin lamince in primary limestone. It occurs everywhere in this 
rock. In addition to this form, it is found in a regular vein in Ticonderoga, varying from six to 
twelve inches in width, in gneiss. This vein contains it, in a very pure state; but it is wrought in 
the cheapest way. The walls of the vein are heated hot, and water thrown upon them in this state. 
In this way it has been explored to the depth of eight or ten feet, for ten rods. This graphite is 
manufactured into pencils of a very good quality. 
22. Sulphate of magnesia, in efflorescences on the tertiary clay. 
23. Porcelain clay, in Minerva. 
24. Hypersthene, forming a constituent part of the rock of the same name. It forms, however, only a 
very small proportion of this rock. 
25. Pearl spar, in small crystals, in the vein of black magnetic oxide of iron at Adirondack. 
It will be observed, that the greater part of all the preceding minerals are contained in, or 
associated with, primary limestone. In this, and in many other facts which I have presented 
in this report in relation to this rock, we see its great importance, and the bearing it has upon 
geological phenomena. 
The preceding minerals fell under my observation while pursuing geological investigations. 
I rarely turned aside for the purpose of searching for them; and considering the field, and 
the little time devoted to them, I hazard nothing in predicting that Essex will prove exceed¬ 
ingly rich in the department of mineralogy. A very large proportion of the surface of the 
county is still uncultivated; it has been examined only in a few isolated points ; the inquiry 
has not been taken up systematically, and therefore we have reason to believe that many dis¬ 
coveries remain to be made. The hypersthene rock, however, which is so extensive, is not 
apparently rich in simple minerals. It appears to be an iron-bearing rock; but when we 
search for clusters, geodes or veins of crystals, we find them entirely wanting, with very 
few unimportant exceptions. The limestone, on the contrary, seems to be loaded with simple 
minerals, though not always fine, yet generally crystallized with several planes in great per¬ 
fection, and with a fine polish. 
Recapitulation of the leading Facts in the Geology of Essex County. 
The principal feature in the geology of Essex, is the great development of the hypersthene 
rock, rising up apparently in the central part of a great chain of mountains, and forming the 
great nucleus around which all the other masses are disposed. 
Another fact equally great, and more important, is the magnitude of the veins of iron ore. 
The greatest amount is connected directly with the preceding rock. I have spoken very in¬ 
definitely on the question whether they are veins or beds, partly for the reason that they appear 
to be contemporaneous masses with the rock itself, and partly because they seem to be closely 
