MINERALOGY OF FRANKLIN. 283 



depth is unknown, hut it may be inferred to be con- 

 siderate, from its rising into hills of upwards of two 

 hundred feet in elevation. This mass varies in its 

 composition — in some places the red zinc ore, in 

 others the Franklin i fee predominates. The red zinc 

 ore abounds at Sterling, where these variations in 

 the nature of the mass can be well observed ; at 

 Franklin, the Franklinite constitutes by far the 

 greater part of the metallic mass ; we perceived in it 

 no signs of internal stratification ; resting upon this 

 bed of Franklinite and red zinc ore, is a bed or lay- 

 er of carbonate of lime and sienite. This is the sub- 

 ordinate bed of limestone which we have already 

 described ; it is irregularly mixed with the sienite, 

 and imbeds masses of it ; it is principally in the cavi- 

 ties or druses of this sienite, that many of the miner- 

 als hereafter to be noticed are found ; these minerals 

 appear in many instances to be of contemporaneous 

 origin with the sienite, but the cavities are filled up 

 with carbonate of lime, which is probably of posterior 

 formation. Upon this bed the sienite is again found 

 without any remarkable character attending it, ex- 

 cept the presence of quartz masses ; in this sienite 

 no other mineral has as yet been observed. All the 

 rocks which we have described are in parallel super- 

 position and are presumed to be of almost contempo- 

 raneous origin. The case is however different with 

 those which we are about to describe. Next to the 

 sienite, but evidently of a later formation, is found 

 a mass of grauwacke of no great thickness. This 



