GALENA LIMESTONE. 305 



the case if one were located in the horizon of the Buff beds, and the 

 other in that of the Blue. The facts here given should assist in avoid- 

 ing mistakes of this kind. The Upper Buff beds furnish the best 

 quality of building stone, unless thick layers for heavy masonry are 

 desired, when the Lower Buff also furnishes good material. Yery 

 little of this formation is well adapted for cutting, though the lower 

 portions of the Upper Buff, and some parts of the Lower, are well 

 suited to rough-dressed, course-work, its soft color, when tastefully 

 relieved by appropriate pointing, cappings, and cornice, producing a 

 very grateful effect. It is a significant fact in this connection, that 

 in the vicinity of Beloit, where, as stated in the local descriptions, 

 quarries have been opened at nearly every horizon of this formation, 

 none are now habitually worked, except those lying in the lower two- 

 thirds of the Upper Buff ~beds. 



This limestone is burned at some localities for quick lime, but ex- 

 cept as a source of local supply when communication is poor, such 

 use is not to be recommended. The ten to twenty per cent, of im- 

 purities which it usually contains are not only so much waste mate- 

 rial, as ordinarily manufactured, but if the heat is allowed to become 

 excessive, the impurities unite with the lime, producing a neutral 

 product. Burned at a low temperature, this difficulty is in a measure 

 avoided. Some of the more impure, yet homogeneous portions, would 

 probably produce a water lime that would fall into the class known as 

 " limes slightly hydraulic," or perhaps a grade higher. 



GALENA LIMESTONE. 



Reposing on the Trenton beds just described, lies the Galena lime- 

 stone; so named from the double fact that in the southwestern part 

 of the state, where it has its most characteristic development, it is the 

 chief formation that bears the lead ore, Galena or Galenite, and that in 

 the vicinity of the city of Galena, it is extensively displayed. 



General characteristics. In chemical constitution, the rock con- 

 sists essentially of carbonate of lime and carbonate of magnesia, united, 

 molecule to molecule, and hence it is, strictly speaking, a dolomite. 

 In addition to these main ingredients, there is always present a vari- 

 able quantity of silicious and aluminous material, and also some 

 iron. Iron pyrites, calcite, zinc blende and galenite are not unfre- 

 quently associated with it in the district under consideration, while 

 in the Lead region these exist in great abundance, and others than 

 those named are associated with them. 



The dolomite of this formation exists usually in an imperfectly 

 Wis. SUB. 20 



