Conklin Quarry, Coralville, Johnson County, Iowa, USA

Field of view: approximately 15mm across. A cluster of brassy millerite crystals 6-7 mm in length. Tim Blackwood specimen and photo.

© Timothy J. Blackwood

Brilliant cubic pyrite crystals to 11 mm with octahedron modifications embedded in limestone beside a fossil brachiopod, probably Spirifer sp. See second photo. Collected 8/2008 on a Cedar Valley Rocks & Minerals Society field trip; photos updated 1/2020.

© 2020 E. L. Clopton

Glassy euhedral calcite scalenohedra to 8 mm with sharp, narrow bands of translucent brown (an organic substance?) included just below certain crystal edges and uniformly stopping just short of each termination. Matrix is compact fossil "honeycomb" coral, probably Favosites sp. Personally collected 8/2008 on a Cedar Valley Rock & Mineral Society ...

© 2020 E. L. Clopton

Sharp octahedral pyrite crystals with brilliant luster and vivid magenta tarnish. Largest crystal is 5 mm on edge. Minor colorless scalenohedral calcite is present. Collected 8/2008 on a Cedar Valley Rocks & Minerals Society field trip.

© 2014 E. L. Clopton

Three very thin tabular crystals of barite, transparent yellowish with opaque white edges collected from the same mud-filled pocket as https://mindat.org/photo-1287091.html . Crystal at left was found broken in two as seen with new barite deposition on the broken edges that prevents them from fitting exactly together. All three crystals show ...

© 2023 E. L. Clopton

Spray of acicular millerite 28 mm tall emerging from a partial calcite crystal. Collected 10/15/2006. Photo updated 12/2020.

© 2020 E. L. Clopton

Closeup of the pyrite crystals.

© 2020 E. L. Clopton

Colorless calcite crystals on limestone host rock. Former John Oostenryk collection. Rolf Luetcke specimen and photo.

Black, single, loose crystals of sphalerite. Former John Oostenryk collection. Rolf Luetcke specimen and photo.

Millerite growing from a chalcopyrite tetrahedron on a calcite matrix. Photographed by and in the collection of Douglas Merson.

© 2020 Douglas Merson

Purchased at the El Paso show ~2001.

© Don Saathoff

Sprays of brassy acicular millerite (color is yellower in person), longest crystals about 28 mm long, on scalenohedral calcite. Collected on a Cedar Valley Rocks & Minerals Society field trip, August 2006, assisted (with sledge hammer) by David Malm. This specimen is a mere shadow of its original self. When found it was spectacular--think of ...

© 2020 E. L. Clopton

Floater crystal of black sphalerite, collected by Marvin Houg of Cedar Rapids, Iowa. See other photos.

© 2021 E. L. Clopton

Thin almost-floater crystal (point of attachment at bottom corner) 25 x 17 x 1 mm, transparent (see second photo) vaseline-tan color with opaque white edges. From the same mud-filled pocket as the crystals in https://mindat.org/photo-518215.html. Collected 8/21/2008 on a Cedar Valley Rocks & Minerals Society field trip. New photo 3/2023.

© 2023 E. L. Clopton

Group of pyrite cubes on quartz. Photographed by and in the collection of Douglas Merson.

© 2020 Douglas Merson

Loose sphalerite crystals. Rolf Luetcke specimens and photo.