Millerite with Calcite

specimen number:
2063395

location:
Cessford Quarry, Dallas City, Hancock Co., Illinois, USA

description:
A massive colorless translucent calcite, this hosting rich crystallized metallic acicular crystals of millerite throughout. This has been etched from the enclosing calcite. The specimen comes with a previous label from the collection of Ray DeMark. Note that his label calls this violarite, but I believe it to be the other nickel sulfide millerite.

Situated near Dallas City in Hancock County, Illinois, the Cessford Quarry exposes Mississippian-age limestone formations, most notably the Warsaw Formation, which are famous throughout the Keokuk region for producing fossiliferous carbonates and mineralized hollow geodes. These geodes developed within sedimentary rock cavities where hydrothermal or groundwater fluids deposited lined crystallizations over millions of years. Commercial quarrying operations focused primarily on crushed limestone aggregate, but the site gained notoriety among mineral collectors for yielding notable specimens of quartz, calcite, and secondary sulfides such as pyrite and sphalerite, along with classic area geodes.

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