An interesting sidenote to this subject....

Several members of Shaler's 27th Arkansas Regiment were detailed to guard the nitre mines in Marion County, and were captured by the Yankees. When exchanged at City Point, Virginia, they made their way to Mississippi. While awaiting transportation across the river back to Arkansas, they got caught in the snare when Grant's army surrounded Vicksburg, and were paroled there after Vicksburg fell. Some of them are listed on the parole list simply as "Nitre Guards", with no regimental designation given. If you happen to run across them while researching the Vicksburg parole list, those are Shaler's wayward boys.

Also, "Kirby Smith's Confederacy: The Trans-Mississippi South, 1863-1865," by Robert L. Kerby, has an overview of mineral resources and mining operations in the TMD.