162 PROCEEDINGS OF THE BOSTON MEETING 



The present paper reviews the synthesis of zinc carbonate; discusses the 

 conditions under wliich normal zinc carbonate (smithsonite) and the basic 

 zinc carbonate (hydroziucite) are formed, as based on analytical chemical 

 data, and discusses in light of the experimental data some of the more im- 

 portant districts in which zinc carbonate ores occur. That limestones and 

 dolomites hydrolyze, the former more readily than the latter because of its 

 greater solubility, is well known ; also that normal carbonates of the alkalies 

 and alkali earth metals produce basic zinc carbonate when added to a solution 

 of zinc sulphate, while the corresponding bicarbonates produce normal zinc 

 carbonate. It has been further shown that excess CO, changes the basic 

 carbonate of zinc into the normal carbonate. These reactions are in agree- 

 ment with the field investigations by Loughlin of some of the oxidized zinc 

 ores in metalliferous deposits of the western United States. The conclusion 

 is reached that the proportion of CO2 present or its bicarbonate radical equiva- 

 lent is the controlling factor in determining which one of the two zinc car- 

 bonates will form — smithsonite or hydroziucite. 



Presented by title in the absence of the author. 



CONTACT-METAMORPHIC DEPOSIT AT THE MOUNTAIN LAKE MINE NEAR SALT 



LAKE CITY, UTAH 



BY AUSTIN F. ROGERS 



{Ahst7^act) 



A detailed petrographic study of a copper-bearing forsterite-magnetite zone 

 at the contact between a granodiorite and limestone. Microscopic examina- 

 tion of thin sections and polished surfaces proves that the minerals were 

 formed in stages one after the other. The sequence of the minerals furnishes 

 a fairly complete history of the deposit. The appearance of tremolite and 

 antigorite and in other deposits sericite, chlorite, talc, and anthophyllite at 

 a late hydrothermal stage is emphasized, for then we have criteria by which 

 the hypogene ore minerals can be distinguished from the supergene ore 

 minerals. Microscopic investigation of the ores of smaller mines and pros- 

 pects is very important on account of the frequent absence of geological data. 



Presented without manuscript, with lantern-slide illustrations. 



NEW AND RARE MINERALS FORMED IN LIMESTONE BY CONTACT 

 METAMORPHISM 



BY ARTHUR S. EAKLE 



{Abstract) 



The crystalline limestone deposit at Crestmore, Riverside County, California, 

 is one of the best and most remarkable examples of localized metamorphism 

 known. In a single quarry there have been exposed, almost daily, zones or 

 bands of new associations of minerals, consisting of new and rare species in 



