GRIMSLEY. | Gypsum Mines and Mills. 59 
the stratum break with a conchoidal fracture. The upper part 
is white, less compact, contains no oval crystals, and pieces 
break more irregularly. 
The occurrence of these selenite phenocrysts is of no little 
interest, as it indicates something regarding the physical condi- 
tions under which they were formed. The frontispiece, and 
also Plate XVI, shows the general appearance of the massive 
gypsum with the selenite phenocrysts included, while Plate 
XXVIII shows a number of detached crystals with their rounded 
edges. The hand level in Plate XVI is 6? inches long, from 
which the size of the crystals can be judged. The crystals 
shown in Plate XX VIII are natural size. 
The existence of such phenocrysts indicates that the ocean 
water at one time was evaporated very slowly, and under the 
most favorable conditions for the production of individual crys- 
tals. Later there was a slight freshening of the water by sur- 
face drainage entering the concentrated lake, so that a partial 
redissolving of the crystals was effected, as shown by the 
rounded edges of the crystals. Still later there was a rapid 
evaporation of the water, precipitating the massive gypsum, 
and an agitation of the shallow water sufficiently vigorous to 
mix the crystals already formed thoroughly with the new pre- 
cipitated gypsum, forming the whole mass as it now appears. 
We have here, therefore, a record of rains and winds not unlike 
those now common to the same locality. 
HOPE MINE. 
At Hope, twenty miles southeast of Solomon, is located the 
mill of the Kansas Cement Plaster Company, which has been 
in operation since 1887. They first used the middle stratum, 
quarried near the top of the hill, one and one-half miles west of 
town. The rock is about 5 feet thick, and lies 10 feet below a 
buff, shaly limestone. The gypsum is white and compact in 
texture, except near the surface, where it is rendered granular 
and more or less colored as a result of weathering. ‘The satin 
Spar associated with it is of clear white color when viewed 
from the side, and viewed from above it possesses a cream- 
vV—) 
