LEONHARD — MILLERHE I.\ ST. LOUIS, ^^-^ 



On the occurrence of Millerite in St. Louis. 

 By Alexander V. Leonhard. 



[Read October, 1SS2.] 



The Millerite is the mineralo^ical specialty of St. Louis ; in no 

 other place has it been found in such abundance and in such 

 beautiful development. The city of St. Louis is underlaid by 

 extensive bed'^ of limestone v^hich belong- to the upper part of 

 the subcarboniferous period, and have bee a termed by Swallov^^ 

 as St. Louis Limestone. A. number of quarries ai-e worked inside 

 the city limits exposing to the eye 40-So feet of the rock strata. 

 In these quarries a great many cavities have been found, ranging 

 in size from less than i inch to c foot and more in diameter, par- 

 tially filled with ditierent minerals. \\\ some quarries certain lay- 

 ers of the limestone contain the largest number of these geodes, 

 but they have been found in all the difterent parts of the forma- 

 tion. Their greater frequency in the so-called '' hydraulic beds" 

 — by which name the gray-colored, softer and porous strata of 

 the limestone are designated by the quarry men — is evidently due 

 to the fact that the solutions depositing the minerals could more 

 easily percolate through these porous strata than through the 

 other parts of the St. Louis Limestone, which are more dense and 

 compact. The following minerals have been found in these cavi- 

 ties : Calcite, Dolomite, Fluorite, Millerite and Sphaler- 

 ite, which form the older series of the minerals, each of them 

 being frequently deposited on the walls of the cavitv directly ; 

 while a younger series of minerals — Anhydrite, Selenite, 

 Barite, Strontianite, and Pyrite — are nearly always formed 

 after and on some of those older minerals. 



The Sphalerite is only very rarely met with, and never in con- 

 nection with Millerite. The Millerite has been formed before, 

 during and after the deposition of the older minerals, of Calcite, 

 Dolomite, and Fluorite. I have never seen Millerite deposited on 

 any of the younger minerals. Barite, Strontianite, and Pyrite, 

 when in connection with it, are alwa\ s formed later. Anhydrite 

 and Selenite are found in the same cavities as the Millerite, but 

 I have not remarked a direct connection between them. 



