South Dakota Mines Museum of Geology

The Museum of Geology is located on the second floor of the O'Harra Building on the campus of the South Dakota School of Mines and Technology (aka South Dakota Mines, aka SD Mines, aka SDSM&T) in Rapid City. The South Dakota Mines Museum of Geology opened in 1885, the same year the school was founded. To my way of thinking, the museum should really be called the Museum of Geology and Paleontology, because over half of its exhibits are fossils from South Dakota, the Northern Great Plains, and Wyoming. I visited the museum in July 2025.

Stomp on over to the Museum

Paleontology

SDM Museum of Geology is located in prime fossil territory. Shale deposits surrounding Rapid City are rich in fossils of Cretaceous marine reptiles, fish, and invertebrates. The White River formation to the east and south yields Eocene and Oligocene mammals. Jurassic dinosaurs come from Wyoming and Utah to the west. And last, but not least, the Hell Creek formation spanning Montana, Wyoming, North and South Dakota to the north is abundant in plant and dinosaur fossils from the late Cretaceous to early Paleogene Periods. This is reflected in the museum's exhibits. It has an extensive collection of Paleogene and Cretaceous fossils, especially mammals from the Eocene and Oligocene Epochs. I picked three exhibits as the focus of this presentation to keep it relatively short: the Badlands Diorama, Brontotherium exhibits, and prehistoric felines.
Okay, so I also threw in a little from the Cretaceous Period.

The Museum obviously has many, many more fossil exhibits. Some of these can be viewed as a slideshow by clicking the following link.

Fossil Exhibits (may take a few seconds to run) Hover cursor over a picture to pause slideshow. Use arrows on a picture to move to next or previous slide.

Paleogene Period 65 to 23 Mya - (million years ago) - "Age of Mammals" - First Period of the Cenozoic Era. The Paleogene Period is subdivided into three Epochs, Paleocene (65-56 Mya), Eocene (56-34 Mya), and Oligocene (34-23 Mya).

Badlands Diorama

The Badlands Diorama displays complete fossil skeletons of fauna from the White River Formation, I'm guessing from the area in and around Badlands National Park. The animals on display are mammals from the Eocene and Oligocene Epochs.

Archaeotherium - Eocene/Oligocene

Protocerus celer (left) and Leptauchenia decora (center right)
late Oligocene herbivores

Leptauchenia decora - a small oreodont herbivore - late Oligocene

Leptauchenia decora and sandstone slab with three animal footprints

Brontotheriidae ("Titanotheres")

The museum has a fine collection of Brontotherium (aka Megacerops) fossils. These mammals were rhinocerus-like herbivores distantly related to horses and tapirs. There are also paintings and sculptures of Brontotherium by artist Charles R. Knight. Knight is famous for his detailed paintings and sculptures of prehistoric animals. I've seen his work in other museums.

Brontotherium fossil - late Eocene

Brontotherium skull

Brontotherium Sculpture by Charles Knight

Prehistoric Felines - Not Your Avereage House Cat

The museum has a fine collection of Felidae fossils (cat family). These belong to the subfamily Machairodontinae which diverged from the ancestors of living cats about 20 million year ago. The fossils displayed in the museum belong primarily to the genus Nimravidae ("false saber cat"). These carnivorous mammals roamed much of North America from middle Eocene to late Miocene. Many of the specimens come from the White River Formation. I might mention a member of another genus called Smilodon, commonly called "saber-toothed tiger".

Big Badlands, Big Bites

Felidae

Nimravidae middle eocene to late miocene

Saber-Toothed "Cats"

Hoplophoenus primaevus (left) and Dinictis felina (right) part of the badlands display

Nimravus brachyops - false saber cat - Oligocene

Cretaceous Period 145 to 65 million years ago - The third and final period of the Mesozoic Era.

Cretaceous Period

Triceratops horridus
South Dakota State Fossil

Edmontosaurus - late Cretaceous

Proper Posture for Edmontosaurus

Mosasaurus conodon - late Cretaceous

Styxosaurus snowii - late Cretaceous

Jurassic Period 200 to 145 million years ago - The middle period of he Mesozoic Era - "Age of Dinosaurs"

Triassic Period 250 to 200 million years ago - The first period of the Mesozoic Era - "Age of Reptiles"

I really didn't find a lot from these periods. Maybe I didn't look hard enough.

Jurassic Period

Triassic Period

Geology and Minerals

The SDM Musuem of Geology has a very extensive mineral collection (thousands of specimens) that have been gathered over the last 100 years. Many of the minerals come from mines that are now defunct and countries that now limit mineral exports. I like the way that the mineral displays are grouped by chemical compound class, ie., sulfates, iodates, etc. As with the Paleontolgy section, I have included just a few photos for the sake of brevity. Click the following link to view lots more (like 100 photos).

Mineral Exhibits (may take a few seconds to run) Hover cursor over a picture to pause slideshow. Use arrows on a picture to move to next or previous slide.

Tungstates, Molybdenates, Chromates

Descloizite - a Vanadate

Sulfates

Metamorphic Rocks

Quartz Geode - Tectosilicates

SD State Mineral (Rose Quartz)
and State Gem (Fairburn Agate)

Fairburn Agates

Chalcedony - Sedimentary Rocks