$8 NEW YORK STATE MUSEUM 



Benson Mines. No shipments were made from this place last 

 year. Changes in the methods of concentration are to be effected 

 before the mines are again placed in operation. 



MILLSTONES 



Millstones are quarried from the Shawangunk grit of Ulster 

 county, one of the few sources of these materials in the United 

 States. The industry was established there many years ago, and 

 during the earliest period of its history was in a flourishing state 

 as the product found a wide sale for the grinding of cereals. This 

 market has been greatly curtailed within the last quarter of a 

 century or more by the general use of the roller mill process for 

 making flour, although some mills still make use of stones for 

 grinding the coarse grains. The small corn mills in the South 

 furnish one of the larger markets for the New York product. 

 Besides millstones, the Ulster county quarries also turn out disks 

 of stone known as chasers which are employed in a roll type of 

 crusher, the disks revolving on a horizontal axis in a circular pan 

 that is sometimes floored by blocks of the same stone. This type 

 of crusher is much used in the grinding of minerals like quartz, 

 barytes and feldspar, and paint materials. 



The Shaw^angunk grit of which the stones are made outcrops on 

 Shawangunk mountain, a monoclinal ridge that extends from 

 Rosendale southwesterly into New Jersey and Pennsylvania. The 

 grit forms the top of the ridge, dipping to the west in conformity 

 with the slope of the surface, and in the Wallkill valley along the 

 north side disappears below shales and limestones which belong to 

 the uppermost formations of the Siluric. The grit rests uncon- 

 formably upon the Hudson River series. In thickness it ranges 

 from 50 to 200 feet. The millstones are quarried within a limited 

 section of the ridge, between High Falls on the north and Kerhonk- 

 son on the south, where the grit appears to be best adapted to the 

 purpose. In character it is a light gray conglomerate with pebbles 

 of milky quartz ranging in size from that of a pea to 2 inches in 

 diameter. The pebbles are rounded and firmly cemented by a 

 silicious matrix of gritty texture. 



The work of quarrying requires only a small equipment, the stone 

 being pried out by hand bars, after the use perhaps of a drill and 

 plugs and feathers. Sometimes a little powder may be employed, 

 but care has to be exercised in its use to avoid weakening the stone. 

 The spacing of the natural joints determines the size of the stone 



