OK, 2380 miles behind us, I'm home. Here's what I have on the mine etc.
Victor Plaster Co. Shaft started 1926. One source shows completed 1927, one source shows 1928. Seam was at 110 feet depth, 5 to 8 feet thick. It was the first shaft mine for gypsum in the US, more often it was quarried. Shaft was 12 1/2 feet square, had a 2-cage hoist. Employed 50 men, used electric drills. 20 mine cars, electric locos, 10 miles of track.
The mine covered 11 to 12 acres by one account. Another source says it extended roughly from the present-day Thruway (which obviously had not been built yet) to Rt 96, and from Rt 332 to Victor limits. Initial output was 200 tons a day, which had doubled by 1936. Gypsum was dumped from the shaft house into the crusher bin, and then weighed and loaded into rail cars. It was high-grade gypsum, used for wall plaster, Plaster of Paris, and as a retainer in cement.
An interesting "scientific"
note - the miners believed the moon caused shot rock to fall at night, so blasting was the last thing done each day.
The mine was closed by 1940, the underground rails were removed, and the shaft filled with water. There were some subsidence issues in the 1950's. A small industrial loco (I believe it was a steam engine) was used for surface switching.
Sources were books by Fisher and by Fagan et al, and personal narrative from a member of the family who subsequently owned the property.
I wonder how many residents of the Plaster Mills Estates trailer park know they are located above old mine workings.
Edit - apparently the forum has a block on words which might offend people and will not let me post the author of one book. The author was Fegan except the second letter should be an "a" instead of an "e".