132 Butler and Schaller — Thaumasite. 



rial with conchoidal fracture that on analysis proved to be 

 composed largely of magnesium carbonate with some calcium 

 carbonate. These magnesite veins, however, were not observed 

 in the Old Hickory mine. 



The Old Hickory mine has been developed to a depth of 

 about 300 feet and four levels have been opened. A vertical 

 shaft extends to the lowest level while the second level, about 

 100 feet deep at the shaft, is connected with the surface by a 

 tunnel. The first level is about 80 feet below the surface and 

 about 20 feet above the tunnel level. On this level the mag- 

 netite body has been opened for a distance along the strike of 

 about 125 feet. To the east of this, from 10 to 25 feet from 

 the magnetite body, a parallel drift has been run in the altered 

 limestone. One hundred feet south of the shaft a crosscut 

 from this drift extends to the east about 25 feet, where it 

 encounters quartzite. Throughout this eastern drift and cross- 

 cut are a great number of veins of white material varying 

 from the thickness of paper to upwards of two inches. To 

 the north of the crosscut many of the veins are open with 

 crystals projecting into the openings while others are composed 

 of a dense white substance completely filling the space. The 

 material from these veins proved on examination to be a mix- 

 ture of quartz and carbonate, the latter probably largely calcite. 

 In the east crosscut just east of the drift and extending across 

 the drift to a crosscut on the opposite side, is a zone of veins 

 having a general northeast-southwest direction, though the 

 individual veins vary in direction and are connected by cross- 

 veins making a network. These are composed of thaumasite 

 completely filling the fissures. 



The Assuring occurred later than the contact metamorphism 

 of the limestone and the filling of the fissures with thaumasite 

 of course occurred at a still later period. The thaumasite was 

 not found associated with the quartz and carbonates in the 

 same veins aud the relative age of the minerals was not deter- 

 mined. At the Paterson, New Jersey, occurrence of thauma- 

 site, the mineral is in trap associated with heulandite, apophyl- 

 lite, laumontite, pectolite, ehabazite, scolecite, and natrolite, the 

 thaumasite crystallizing later than the zeolites. No zeolites 

 were found associated with the thaumasite at the Old Hickory 

 mine, though these were especially looked for. It seems prob- 

 able, however, that the mineral w T as found under physical con- 

 ditions similar to those favorable to the formation of zeolites. 



Physical Characters. 



In the hand specimen the thaumasite from Beaver County 

 is a nearly pure, white mineral with silky luster due to its 



