638 Jenkins — Spotted Lakes of Epsomite in 



Aet. XXXI. — Spotted Lakes of Epsomite in Washington 

 and British Columbia; by Olaf P. Jenkins. 1 



Since April, 1916, large quantities of natural epsom 

 salts have been mined and shipped from the so-called 

 "Spotted Lakes " — two briny lakes, one in Washington 

 and one in British Columbia. These lakes are both on 

 Kruger Mountain, near the international boundary, and 



Fig. 1. 



Fig. 1. — Large spotted epsomite lake in British Columbia, on Kruger 

 Mountain. Photograph taken during the dry season in July, 1917. 



within a few miles of each other, north of Oroville, Wash- 

 ington. The lakes have no outlets and the material 

 occurs as a precipitation from the evaporation of waters 

 saturated with magnesium sulphate. The mineral formed 

 is epsomite, MgS0 4 .7H 2 0. 



The accompanying figures show why these lakes are 

 ordinarily described as being spotted. The dark spots 

 represent shallow pools of brine, immediately beneath 

 which are solid rock-like masses of epsomite. The areas 

 between the dark spots are white because they are dry, 



1 This examination was made by the writer while engaged in work for 

 the Washington State Geological Survey during the summer of 1917. 



