Barite and Calcite from the Minerva No. 1 Mine, Cave-In-Rock, Illinois

Contributed by: Chris Clemens
minID: K65-7N6
Date: Apr 15th, 2026
Locality: Minerva No. 1 Mine, Ozark-Mahoning group, Cave-In-Rock Mining Sub-District, Hardin County, Illinois, USA (See on Mindat)
Size: 11.8 x 4.6 x 15.6 cm
Weight: 490 g

Description:
This very delicate and aesthetic specimen is from the historic Minerva No. 1 Mine in the Illinois-Kentucky Fluorspar District of Southern Illinois, located in Cave-In-Rock, Hardin County, Illinois. This piece features delicate bladed crystals of barite sitting on top of interspersed calcite crystals on a limestone matrix. Minor fluorite is also present.

When viewed under midwave UV (305 nm), the barite shows a bright white response, and the calcite fluoresces a beautiful pastel pink. The limestone matrix is not fluorescent. This specimen is at its best when viewed under mid wave UV.

Under shortwave UV (254 nm) the barite shows pale blue-white fluorescence while the calcite shows a moderate orange response.

An underlying layer of purple, fluorescent fluorite becomes visible under long wave UV (365 nm), while the barite shows a white response and the calcite fluoresces a moderate to dim peach/orange.

The last picture shows the specimen under visible light. Delicate bladed crystals of colorless barite sit on top of interspersed pale yellow/amber calcite crystals on a limestone matrix. An underlying layer of purple fluorite is also present.

Originally posted by Chris Clemens on Nature's Rainbows in 2023.