Excerpts from: The Gypsum of Michigan and the Plaster Industry, by G. P. Grimsley, Published by authority of the laws of Michigan under the direction of the Board of Geological Survey, Lansing, Robert Smith Printing Company, State printers and binders, Illustrated, 1904, 247 pages (page excerpts 36, 105-106, 124 and 160)
William T. Powers’ plaster mine, Gypsum Products Manufacturing Company at the terminus of the West Side Water Power Canal near the west end of the G. R. & I. Railroad bridge.
In November 1894, William T. Powers began constructing a gypsum mine one hundred feet below the bed of the Grand River. The mine shaft was located at the most westerly span of the Blue Bridge, formerly the Grand Rapids & Indiana Railroad Bridge. Powers owned land on the west bank, extending from where the bridge crossed the river to the Sixth St. bridge. At a depth of 60 feet a vein of plaster rock six feet in thickness was discovered. Immediately beneath this an extremely fine quality of plaster rock twelve feet thick ran under the river as far north as the Sixth St. Bridge.
The surface of the deposit was mapped and divided into squares about twenty feet each. Four of these were excavated and the fifth left to support the roof. In this way timbering was avoided and there was no danger of the roof caving in.
State law prescribed the manner in which the mines were worked. Pillars twenty-five feet square were maintained to support the roof of the mine. Then it was permitted to cut out the rock within a radius of twenty feet of each pillar. The roof could also be mined as there was a hard rock basis to the river bed.
The original area Powers mined covered about nine acres extending from the Pearl Street bridge to the Fulton Street bridge. Cubic tons of gypsum were brought up the mine shaft daily to be converted into plaster and shipped all over the world.
When the plaster rock was mined is contained about 17 per cent water and it was necessary to remove it in order to make it a usable building material. The rock was first crushed, then ground between mill stones in the same manner that wheat was ground. The plaster flour was put into great pans holding eight to ten tons and heated until it boiled. During the process of boiling the plaster flour assumed the appearance of water with white coloring in it, but as soon as the water of crystallization was driven off the movement ceased and the plaster dropped to the bottom of the pans.
Mention Grand Rapids and people think of furniture, but that was not our first important industry. It was gypsum, or plaster, discovered in extensive surface beds along the creek named for its discovery—Plaster Creek.
1880–1890s — Powers owns a gypsum mine in Spearfish, Dakota Territory
1894 — Sat 17 Nov — Sink Plaster Mine Shaft (18941121 Grand Rapids Herald — Manufacture Marble)
1896 — Tue 2 Jun — Gypsum Products Manufacturing Company files articles of incorporation
1898 — Calcining apparatus– Powers’ US Patent #618902
1900 — Agitator for calcining-kettles – Powers’ US Patent #670597
1903 — Sat 4 Apr — Fire
1903 — Mine rebuilt after the fire
1904 — Mine partially fills with water and takes nine days to pump dry
1905 — In September the mine is still full with flood waters since a June freshet
1909 —Jun 17 — William Thompson Powers dies
1909 — Gypsum Removal Ceases
1912 — Sanborn Fire Insurance map shows wood fibre (excelsior) making (1st floor) and storage of cotton batting (2nd floor) for Hot Blast Feather Company mattresses
1913 — In November The Kalamazoo Interurban purchases the mine and property
1913 — Mill and the buildings are junked and dismantled, but not demolished.
1915 — The buildings of the mill still appear to be standing in the 1915 panoramic photo
2017 – Dec — Mine shaft collapse in what is nowGVSU Downtown Campus, Lack’s Park
2018 – Jan 4 — WOOD TV 8 News Article
photo courtesy Grand Rapids City Archives, Community Archives and Research Center (CARC), Smoke Department Collection, Louis C. Towner, 1911, Neg. #4069.