Minerva No. 1 Mine, Cave-in-Rock, Hardin Co., Illinois, USA
A rich, cabinet sized specimen of this strontium carbonate from the Illinois Fluorspar District. Although the area was best known for its fluorite specimens, it also produced a number of rare (relatively) carbonates-- alstonite, benstonite, witherite, strontianite, etc.
The Minerva #1 Mine closed in 1996.