228 Field Columbian Museum — Geology, Vol. i. 



EPSOMITE. 



NEAR WILCOX STATION, 65 MILES NORTH OF LARAMIE, WYOMING. 

 MUSEUM No. M 6126. 



An account of the above occurrence of epsomite was given the 

 writer by Prof. W. C. Knight of the University of Wyoming, in a 

 recent letter. He writes: "A deposit of epsomite, which is of 

 variable depth, covers an area of 90 acres near Wilcox Station, 

 Albany County, Wyoming. In the spring the area is covered with 

 water to the depth of a foot or more, forming a small lake, but on the 

 advent of summer the water evaporates rapidly and an abundant 

 deposit of beautifully crystallized epsomite is left." 



A few of these crystals were received from Prof. Knight at the same 

 time by the writer, but not being able to study them immediately, 

 they became, through deliquescence, unfit for thorough crystallographic 

 investigation. I have thought it desirable, however, to publish an 

 account of the occurrence so that any who may visit the locality may 

 improve the opportunity to secure material whose forms may admit 

 of exact determination. The crystals received by the writer are from 

 8 to 15 mm. in length and are of elongated prismatic habit. Many 

 are doubly terminated and have pyramidal planes which plainly show 

 sphenoidal symmetry. The habit of the crystals and the fundamental 



Fig. 6— Epsomite. 



forms are shown by Fig, 6. The determination of the pyramid 

 z (in) depends on a measurement secured as follows : 



Measured. Calculated. 



m. -z= 1 10: in — 50° 30' 50° 55' 



While some of the crystals have only the simple development 

 represented in the figure, others are evidently more highly modified, 

 but owing to the deliquescence previously referred to, it was found 

 impossible to determine the forms. 



