I08 LOWER PENINSULA, 



covered, but on the western edge of the belt we meet again with 

 large gypsum deposits in the vicinity of Grand River. The gypsum 

 formation is found close under the drift extending from the south- 

 ern limits of the city line of Grand Rapids to within a mile or 

 more south of the village of Grandville, covering in all about 

 6 or 8 square miles, and found everywhere over that space 

 within a distance of not more than 50 feet from the surface. 

 Some spots there may be found where the gypsum beds have been 

 destroyed during the drift period, but, as a rule, it may be with 

 safety looked for everywhere in the district. Seven gypsum quar- 

 ries are now in operation in the vicinity of Grand Rapids, situated 

 on both sides of Grand River, and if the demand for gypsum were 

 to increase tenfold, there would still be no lack of material. 



In most of the quarries, a bed of pure gypsum much cut up by 

 erosions is found close under the drift ; below that bed are dark 

 gray shales with seams of argillaceous limestones and arenaceous 

 beds, amounting to various thicknesses, in different localities ; 

 then follows a gypsum bed from 8 to 12 feet in thickness, and 

 under it are again shales and limestone beds with thin seams of 

 gypsum. 



In the plaster quarries of the Grand Rapids Plaster Co., on the west 

 side of Grand River, the upper layers in the bluff are soft arenaceous 

 shales, interlaminated with seams of limestone and arenaceous flag- 

 stones, having an abundance of globular or lenticular nodules of 

 rose-colored granular gypsum, as well as seams of a brown gypsum, 

 in large, columnar crystals, together with thin seams of a perfectly 

 colorless, translucid selenite. At the base of the bluffs, two thick 

 beds of gypsum project, partly composed of pure white or reddish 

 granular gypsum with gray, veinous, mottled seams ; partly of a 

 more impure brecciated mass of gypsum and gray limestone 

 cemented together, which latter, if the limestone is mingled in 

 undue proportion, has to be thrown aside as waste rock. In this 

 locality, the gypsum is mined by driving subterranean galleries 

 into the bluff. A view of the mine is represented in the plate 

 accompanying this report. A large plaster mill is erected close 

 to the mine, where the impurer gypsum is ground for agricul- 

 tural purposes, the purer rock being selected and ground separate- 

 ly for conversion into plaster-of-paris, while the finer granular 

 masses are occasionally used for ornamental purposes, such as the 



