STRATIGRAPHY AND STRUCTURE CASTLETON AREA VERMONT

varieties for the market on the basis of shade and permanence of color.
A modern discussion of commercial subdivision of the Mettawee slate
is available by D. M. Larrabee (1939-1940). This slate is used for roofing,
for ornamental paving, and in the manufacture of asphalt shingles.
Problems in slate quarrying are fully discussed by Dale (1899) and
Larrabee.
Roughly the eastern third of the Castleton quadrangle lies in the
Vermont marble belt, which stretches from Danby at the south to
Brandon at the north. North of Brandon the grain-size of the calcareous
rocks is smaller, and the rocks are more properly called limestones.
Among the rock units discussed in this report the Boardman formation
(Sutherland Falls marble and Columbian marble members), the Bascom
formation, the Burchards limestone, the Beldens formation, the Orwell
limestone, and the Whipple marble have all been quarried either for
building stone, land lime, or calcined lime. At present most of the building
stone quarried here comes from the white and gray-streaked Columbian
deposits and from the several green-streaked marbles of West
Rutland that have been grouped here into the Beldens formation. Some
Whipple marble is quarried along with the Columbian at Clarendon
Springs. The Sutherland Fa'ils marble and some of the lower Bascom
are at present quarried for lime at Florence. For a thorough treatment
of the geological aspects of the marble industry the reader should consult
one of the reports dealing particularly with the marbles of western
Vermont. Among these are those of Bain (1931, 1933, 1934, 1938), Dale
(1912), and several papers to be found in earlier Reports of the Vermont
State Geologist.
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