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[ASSEMBLM 
Of calcareous tufa, which may be ranked among the useful minerals, 
Herkimer county has several important localities. One of the most 
remarkable is that near the head of the Otsquaga creek, where there 
is a single mass about 300 feet long, 50 wide, and from 10 to 40 
thick ; and this is constantly increasing in size by the percolation of 
water charged with carbonate of lime.* There are also a few sulphur 
springs in this county, from one of which sulphuretted hydrogen is so 
abundantly evolved, that when fired it will continue to burn on the sur- 
face of the water. 
This county has been known to mineralogists in consequence of its 
numerous localities of rock crystal, or false diamond, as it is sometimes 
called. The best locality at present known is at Middleville, and Mr. 
Vanuxem in noticing it, has justly observed, that there is probably no 
place in the world where these crystals are found more numerous, 
more perfect and more beautiful. They are of various sizes, and often 
exhibit new and interesting crystalline forms. Some of these have 
been already described in the recent mineralogical works of Shepard 
and Dana, but several others have been obtained of which figures will 
be given in my final report. Not the least curious circumstance con- 
nected with these crystals is, that they frequently contain a liquid 
which is probably bituminous, from the yellowish stain which it leaves 
in the cavities after it has evaporated. Sometimes the crystals instead 
of having two perfect terminations, are connected at one end to the 
rock, presenting surfaces studded with pyramids of the highest finish. 
The following may be added to the minerals of this county : 
Sulphate of barytes, lamellar and sometimes fetid — Near Little Falls 
and Fairfield. 
Graphite. 
Alum and alum slate. 
Tourmaline. 
Coccolite — In bowlders. 
JEFFERSON COUNTY. 
Regarding only its mineral resources, this is undoubtedly one of the 
richest counties in the State. The ores of iron are of course the most 
important, and they are found in great abundance. Of the specular 
iron or red oxide, which is the most common, there are here and in the 
* Eaton's Canal Rocks, p, 128. 
