Statistics for occurrence #1 of “Castleton, Vt.” in chapter 19, entry slatepencil of Knight's Mechanical Encyclopedia:

...n, are made in Germany. These have been pretty much superseded in this country by the softer, neater, and greatly superior article, known as soapstone pencils, made from a peculiar stone found near Castleton, Vt. This stone contains over 50 per cent of silica, a large proportion of alumina, and also some potash and iron; and, while having some resemblance to soapstone, more nearly resembles slate in texture ...
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