G. C. Broadhead o?i Barite crystals. 419 



Logan. The observations of Mr. Wing afford nothing to sustain 

 the view that there was an epoch of disturbance in the return at 

 the close of the Primordial or Cambrian period, hut, on the con- 

 trary, they prove that the rocks went on forming in n-gular sue- 

 cession nearly or quite to the close of the Lower Silurian ; and 

 that then followed. :i> Mr. Wing concludes, the epoch of upturn- 

 ing and metamorphism. The making of the Given .Mountains has 

 for many years been referred by some geologists to this epoch, on 

 the basis of the fossils in the limestones ot Vermont. These 

 fuller developments leave no doubt that this view is right, at least 

 so far as the Eolian limestone of Vermont and the associated 

 schists and quartzyte are concerned. 



In another number of this Journal I will close this subject by 

 stating the bearing of the Vermont facts on the geology of Kerk- 



Abt. XLIY.— On Barite crystals from the Last Chance Mine, 

 Morgan County, Missouri; and on Obthitefrom Adair County, 

 Missouri; by G. C. Beoadhead. 



I. Barite from Morgan County, Missouri. 

 The rocks of the barite locality in Morgan County, Missouri, 

 are of the age of the Second Magnesian Limestone. A shaft has 

 been sunk in a spring through masses of tumbled rock display- 

 ing what seemed, in Missouri miners' parlance, to be a "circle " 

 of about twenty feet diameter. This " circle " was found to 

 be filled with fractured masses of limestone, sandstone and 

 clay for forty feet in depth, or to the bottom of the shaft when 

 I netted it. These masses of rock were often found studded 

 over with beautiful crystals of barite. "Pbe galenite was also 

 often covered with such crystals. In some cases a thin coating 

 of transparent barite covered the rock to which the crystals 

 adhered, but they were often seen loosely adhering to the 

 naked rock. 



The form of these crystals is different from any heretofore 

 found in Missouri. They are elongated into prismatic forms 

 (H) in the direction of the macn ire attached 



to the rock by one of its extremities. The development of the 

 basal plane gives them a flattened appearance. The free ex- 

 tremity of the crystals is gradually sharpened off r 

 edge through the presence of very low macrodome. This is so 

 irregularly developed, however, as not to admit of tragi 

 measurements, but seems to have the symbol f i The central 

 portion of all the crystals toward the attached extr- 

 perfectly transparent. This clear portion has a rhombic form 

 corresponding to the fundamental (cleavage) prism, and is 



