Diamond-drill exploration of the Rousseau talc prospect, Cambridge, Vermont, and the Barnes Hill prospect, Waterbury, Vermont

Abstract

The Geological Survey carried out a program of diamond-drilling at two localities in Vermont during the period July-September 1950. The deposits chosen for drilling were two of the more promising talc deposits associated with ultramafic rocks of several that had been mapped earlier by the Geological Survey, but could not be evaluated accurately because critical data were lacking that could be obtained only by sub-surface exploration. The Rousseau talc prospect is in Cambridge township, Lamoille County, Vermont. Surface rights are owned by L. and N. N. Porter; mineral rights are owned by Eastern Magnesia Talc Co. Three drill holes encountered no talc; the other five penetrated from 2 to 110 feet of talc ore. The deposit lies on the west limb of the Green Mountain anticlinorium. The country rock consists of quartz-chlorite-sericite schist and chlorite-albite schist. The schistosity strikes slightly west of north and dips 20° - 40° to the west. The talc deposit is roughly lenticular, and although generally concordant in detail with the schistosity of the country rock, is slightly cross-cutting in overall relationship. The entire deposit is composed of Tit (talc-carbonate rock) and steatite, out is presumably derived from ultramafic igneous rooks which were first serpentinized. The dimensions of the lens are about 700 feet by 500 feet by 130 feet. The talc is of good quality and is suitable, either as a mine run product or as a flotation concentrate, for most industrial uses other than industrial steatite. No pencil stock was encountered. The Barnes hill talc prospect is in Waterbury township, Washington County, Vermont. Surface rights are divided among Donald P. and Glenola Brown, John Barnes, and Eastern Magnesia Talc Co. One drill hole at Barnes hill was barren. The other six penetrated about 20 to 140 feet of talc ore. The deposit lies on the east limb of the Green Mountain anticlinorium. The country rock outside of the ultramafic rock body consists of quartz-chlorite-sericite schist, chlorite-albite schist; and chlorite amphibolite, which strike generally about N, 20° E. and dip steeply to the east. The ultramafic body is elliptical in plan, about 1,600 feet long and 360 feet wide. The vertical dimension is unknown. The original ultramafic rock has been almost completely serpentinized and is extensively altered to grit and steatite. The talc ore is somewhat irregularly distributed throughout the ultramafic body, but it is possible to delineate with considerable confidence portions of the body that consist predominantly of ore. The largest ore bodies are in the eastern and northern parts of the ultramafic body. The ore contains more or less admixed serpentine, and so is only of intermediate to fairly good color (whiteness). It is suitable for many industrial uses in which purity and high whiteness are not necessary. No pencil stock was seen.