Wyoming is an extraordinary state for rockhounding. The state has enormous deposits of low-sulphur coal (and the world’s largest surface coal mine complex, located near Gillete) and leads the U.S. in the production of coal, bentonite, and trona. Wyoming, of course, also has a storied history for dinosaur fossils and the east coast collecting expeditions that ran roughshod over the state. Portions of the fabled Como Bluff site remain, but many of the extraordinary dinosaur fossils were removed and shipped east. Today, however, Wyoming is home to huge tracts of federal public lands (the BLM manages approximately 18 million acres of federal public lands in Wyoming) and nearly every county has a wide variety of interesting rocks, gemstones, minerals, and fossils. In addition, Wyoming is home to our nation’s premier national park – Yellowstone – and its fantastic geologic features. Wyoming also is home to significant national monuments that feature extraordinary geologic formations. In the central part of the state, varied rocks layers covering approximately four billion years of time are evident. Highway 20 between Shoshoni (Fremont County) and Thermopolis (Washakie County) includes signs identifying the various rock layers – one of the most unique places in North America.
State Rocks, Gemstones, Minerals, Fossils, & Dinosaurs
Rockhounding Tip: Knowing state rocks, gemstones, minerals, fossils, and dinosaurs often can be very useful information for rockhounders. Ordinarily, states with significant mineral deposits, valuable gemstones, fossils, or unusual or significant rock occurrences will designate an official state mineral, rock/stone, gemstone, fossil, or dinosaur to promote interest in the state’s natural resources, history, tourism, etc. Accordingly, such state symbols often are a valuable clue as to potential worthwhile rockhounding opportunities.
Gemstone: Jade (1967)
Wyoming designated jade as its official state gemstone in 1967. Jade is a compact, opaque gemstone ranging in color from dark green to almost white. The term ‘jade’ is applied to specimens cut from the minerals jadeite and nephrite. Wyoming's state gemstone is of the nephrite variety. Nephrite, a member of the amphibole group of minerals, is a silicate of calcium and magnesium, with a small amount of iron replacing part of the magnesium. It is a tough, compact variety of the mineral tremolite. Nephrite’s color depends on the amount of iron present. Nephrite is usually some shade of green: it may range from sea green, gray green, celadon, lettuce green, grassy green, and spinach green. Other colors of nephrite include blue gray, reddish gray, greenish gray, yellow, and black. The famed Wyoming jade fields occur in a rectangular band that runs roughly from Lander southwest to Farson, down to the Red Desert in Sweetwater County, east to Seminoe Dam, north to Alcova, and westward back to Lander. The 1930s and 1940s were the "glory days" of jade hunting in Wyoming. Many sources cite 1936 as the year of jade discovery near Lander. From 1936 until 1945, Wyoming residents primarily hunted for jade. The end of World War II plus a 1945 article in Popular Science titled "Green Gold of Wyoming" changed that – the publicity created intense competition for Wyoming jade.
State Fossil: Knightia [fish] (1987)
Wyoming designated Knightia as its official state fossil in 1987. Knightia is an extinct genus of fish well known from abundant fossils found in the Green River Formation of Wyoming. They rarely exceeded ten inches in length and are found throughout the formation. Knightia was a slender fish and seems to have been a secondary consumer, feeding mainly on ostracods, algal forms, and diatoms, as well as some smaller fish. They were schooling fish, and because of this they are frequently found together in mass mortality layers. Knightia lived in several large lakes that existed near the junction of Wyoming, Utah, and Colorado during the Eocene Epoch, some 50 - 40 million years ago. At that time, the climate of Wyoming was warm and tropical, instead of the arid badlands of today. The Eocene lake system consisted of three lakes, Uinta, Gosiute, and Fossil. Most of the best fish fossils come from Fossil Lake. They occur in mass die-offs, sometimes as many as several hundred fish densely packed in a single square yard of Green River rock. Because of this, Knightia is the most commonly collected vertebrate fossil in the world, and is frequently sold in souvenir shops across Wyoming and throughout the United States. It is thought that low oxygen conditions led to the death of large schools of fish, that settled to the lake bottom and were quickly buried and fossilized. Missionaries began reporting fish fossils as early as the 1840s. Explorer James Hall and fur trapper Jack Robinson wrote of them in 1848, and the first published report appeared in 1856 authored by Philadelphia paleontologist Joseph Leidy. Rich exposures of fish fossils were exposed during the building of the Union Pacific Railroad. Today, part of the area is preserved as Fossil Butte National Monument near Kemmerer.
Wyoming is unique. Wyoming did not enact a state law specifying an official state dinosaur. Rather, Wyoming enacted a law specifying an election to determine the state’s official state dinosaur. Accordingly, in 1994, students voted to make Triceratops the official Wyoming state dinosaur. It won with 70 percent of the vote, crushing opponents Apatosaurus, Megalosaurus, and Diplodocus. Triceratops had three horns on its skull - one on its snout and one above each eye. The name is derived from the Greek words treis, "three"; kerat, "horn"; and ops, "face." Triceratops was one of the largest horned dinosaurs and roamed the land that is now Wyoming near the end of the Cretaceous Period, some 68 - 65 million years ago, as the Western Interior Seaway that divided the continent was retreating to the south. Triceratops belonged to a diverse group of ornithischian ("bird-hipped") dinosaurs called ceratopsians characterized by a large frill at the back of the skull and a varying number of facial horns, that populated North America and Asia toward the end of the age of dinosaurs. Many different ceratopsians have been described, but of these, Triceratops is the best known and most familiar. It was a large, quadrupedal herbivore that fed on tough, low growing vegetation. Although a complete skeleton has never been found, many good skulls have been, and enough other bones of Triceratops are known for scientists to deduce that it was about twenty-five feet long and weighed around five tons. The first Triceratops specimen was discovered in Wyoming in 1887. It was originally thought to be an extinct type of bison, and only later recognized as a dinosaur. Since that time, many other Triceratops fossils have been uncovered, primarily in the Hell Creek Formation in the Black Hills region of South Dakota, eastern Wyoming, and Montana.
State-specific rockhounding books (including the books listed here as well as other books), regional rockhounding site guides, and other helpful rockhounding resources are identified - by category - in the Books & Gear section of Gator Girl Rocks with a link to the Gator Girl Rocks Amazon Store where you may easily browse selected resources and securely place an order. Your order will benefit Charity Rocks!
Wyoming State Mineral & Gem Society
The Wyoming State Mineral & Gem Society’s website is an excellent resource for rockhounding Wyoming.
- Darwin Spearing & David Lageson, Roadside Geology of Wyoming (2d ed., 1988).
- William Fritz, Roadside Geology of Yellowstone Country (1st ed., 1985).
- Kenneth Lee Graham, Rockhounding Wyoming (1996).
- W. Dan Hausel, Gems, Minerals, & Rocks of Wyoming: A Guide for Rock Hounds, Prospectors, & Collectors (2009).
- H.C. Dake, Northwest Gem Trails (2d ed., 1956 – originally published in 1950).
- Allan W. Eckert, Earth Treasures Vol. 3 - Northwestern Quadrant (1986; reprint in 2000).
- James Martin Monaco & Jeannette Hathway Monaco, Fee Mining & Rockhounding Adventures in the West (2d ed., 2007).
- Kathy J. Rygle & Stephen F. Pedersen, Northwest Treasure Hunter's Gem & Mineral Guide (4th ed. 2008).
Museums of Interest to Rockhounders
University of Wyoming – Laramie, Wyoming
The UW Geological Museum features a variety of displays to illustrate Wyoming's past environments, highlighted by a 75-foot Apatosaurus (Brontosaurus) skeleton that dominates the museum's exhibit hall (it originally was collected for the Carnegie Museum). Another highlight is "Big Al," a display of the most complete Allosaurus fossil ever found. Hundreds of rock and mineral samples from throughout Wyoming's geological history are also displayed. Outside the museum, a life-size Tyranosaurus rex has stood for decades.
Tate Geological & Mineralogical Museum
Casper College – Casper, Wyoming
The Tate Museum exhibits include "Dee," the largest mounted Columbian mammoth in North America, and a good selection of other Wyoming fossils including marine forms and mammals.
The Wyoming Dinosaur Center
Commercial (fee access) business. The Center displays many high quality specimens from both in and out of state, including an Archaeopteryx from Germany and the Supersaurus "Jimbo.” The center maintains a working quarry open to the public during "Dig for a Day" events.
Western Wyoming Community College
Rock Springs, Wyoming
Western Wyoming Community College is home to five life sized dinosaur displays. They are the largest easily accessible collection of dinosaurs along Interstate 80 from Chicago to San Francisco. In order to bring Wyoming dinosaurs back to Wyoming, a fund raising project began in 1989 to collect and display specimens native to Wyoming from throughout the Jurassic and Cretaceous periods of the Mesozoic Era. The dinosaurs on display are: Camptosaurus (displayed near the bookstore) which was originally found in the fossil dinosaur beds at Como Bluff in 1879; the giant Plesiosaur which lines the hall way leading to Mitchell's Dining Hall; Stegosaurus – which is one of the first dinosaurs found in Wyoming in 1878 at Como Bluff; Triceratops - which was discovered in eastern Wyoming near Lance Creek in 1889; and the mighty Tyrannosaurus watches over the diners at the T-Rex Grill. All of the dinosaur displays are free and open to the public whenever the college is open.
Wyoming State Museum
The Wyoming State Museum includes permanent exhibits regarding Wyoming’s extensive coal deposits as well as dinosaur fossils.
Washakie Museum & Cultural Center
Museum exhibits include the earliest mammoth kill site in North America (the Colby Mammoth Site).
The Saratoga Museum includes local and other rock, gem, mineral, and fossil exhibits, including Wyoming jade.
Fossil Country Museum
This museum, in coal country, includes a replica coal mine. On a personal note, this museum did an extraordinary favor for our family. After we got soaked – and completely muddy – searching for fish fossils, the museum kindly let us clean up in their restrooms. We then enjoyed a terrific museum tour (and even bought some fish fossils for friends).
Places to Visit - Interesting Sites To See
Yellowstone National Park
Wyoming is home to the vast majority of America’s First National Park. Yellowstone National Park is amazing. Among the park’s over two million acres, visitors can see fossilized trees, geysers, hot springs, bubbling mudpots, steaming fumaroles, travertine formations, and obsidian cliffs – all within an ancient, but still active, giant volcanic caldera. Yellowstone National Park is home to one half of the world’s geothermal features. Its more than 300 geysers make up two thirds of all those found on earth. Most of the park is well over a mile above sea level (actually over 7,500 feet above sea level).
Grand Teton National Park
Grand Teton National Park – just south of Yellowstone National Park – protects several of the majestic peaks of the Teton Range. The Park includes some of the most ancient rocks found in any of America’s National Parks. The oldest rocks dated so far are approximately 2.68 billion years old (but even older rocks are believed to exist in the Park). Formed during the Archean Eon, these metamorphic rocks include gneiss, schist, and amphibolites. Metamorphic rocks are the most common types found in the northern and southern sections of the Teton Range. Approximately two and a half billion years ago, the metamorphic rocks were intruded by igneous granitic rocks that now are visible in the central Tetons including Grand Teton and the nearby peaks. The light colored granites of the central Teton Range contrast with the darker metamorphic gneiss found on the flanks of Mount Moran to the north. Magma intrusions of diabase rocks 765 million years ago left dikes that can be seen on the east face of Mount Moran and Middle Teton.
Fossil Butte National Monument
West of Kemmerer in Lincoln County, Wyoming
Fossil Butte National Monument preserves the best paleontological record of Tertiary aquatic communities in North America and possibly the world, within the 50-million-year-old Green River lakebeds. Fossils preserved, including fish, alligators, bats, turtles, dog-sized horses, insects, and many other species of plants and animals suggest that the region was a low, subtropical, freshwater basin when the sediments accumulated, over about a two million-year period. The fossils are exceptional for their abundance, variety, and detail of preservation.
Devils Tower National Monument
Crook County, Wyoming
Devils Tower is an igneous intrusion (laccolith) located in the Black Hills of Northeastern Wyoming in Crook County (some geologists, however, believe that it is a volcanic plug). The surrounding rock is sedimentary and, over millions of years, has eroded away. Devils Tower rises approximately 1,260 feet above the surrounding land (the summit is nearly one mile above sea level). Devils Tower National Monument was the first established National Monument in America. President Theodore Roosevelt established it in 1906.
Independence Rock State Historic Site
Natrona County, Wyoming
Independence Rock is a large granite rock, approximately 120 feet high. During the 1800s, the rock was a prominent and well-known landmark for pioneers along the emigrant trails (Oregon Trail, Mormon Trail, California Trail). It was designated a National Historic Landmark in 1961. The rock derives its name from the fact that it lies directly along the route of the emigrant wagon parties bound for Utah, Oregon, or California, which usually left the Missouri River in the early spring, attempted to reach the rock by Independence Day, July 4, in order to reach their destinations before the first mountain snowfalls in autumn.
Red Gulch Dinosaur Tracksite
Southeast of Shell, Wyoming
The tracksite is located on federal public lands managed by the Bureau of Land Management. The site features about one thousand middle Jurassic dinosaur tracks in limestone. The site includes extensive interpretive signs for a self-guided tour of the site. Admission is free. Travel about eight miles east of Greybull, Wyo. or four miles east of Shell on US Highway 14 to the Red Gulch/Alkali National Back Country Byway turnoff. Head south on the byway, a dirt road, about five miles to the tracksite.
Cottonwood Creek Dinosaur Trail
Southwest of Casper near Alcova Reservoir, Wyoming
This trail is located on federal public lands managed by the Bureau of Reclamation. The trail leads through the Jurassic Sundance and Morrison formations. Fossils are present but must be left "in situ" for other trail users to view. To get there, take Highway 220 southwest from Casper to Alcova Lake, turn left at the town of Alcova and follow the road around the east side of lake. After passing the Black Beach turnoff, turn right at the dinosaur sign and stop in the parking area. The trail, with easily followed interpretive signs, is always open unless weather has forced road closures. Admission is free.
Como Bluff Dinosaur Graveyard
East of Medicine Bow, Wyoming
In 1877, employees of the Union Pacific Railroad found large bones weathering out of the hills at Como Bluff near Medicine Bow, Wyoming, and wrote to paleontologist Othniel C. Marsh of Yale College, in Connecticut. Within a year, diggers hired by Marsh and teams working for paleontologist Edward D. Cope, of Philadelphia were excavating tons of fossil bones for shipment east. Marsh and Cope were bitter professional rivals, and the same spirit infected their employees. Diggers smashed bones in the quarries of the other teams and even in their own to avoid thefts. No one will ever know what valuable specimens were lost to this rivalry, but the ones that were gained include Dryolestes, the first Jurassic mammal discovered in North America; large pieces of Apatosaurus, then known as Brontosaurus; several Baptanodons—marine reptiles; and many others. Specimens collected for Marsh went to the Peabody Museum at Yale; those gathered for Cope went mostly to the Academy of Natural Sciences in Philadelphia.
Fossil Cabin Museum
Highway 30 – near Medicine Bow, Wyoming
This roadside attraction no longer is open for tours, but the building still exists. The building was built out of 5,796 mortared-together dinosaur bones that were dug out of a nearby ridge known as Como Bluff. The Boylan family -- Thomas, wife Grace, and son Edward -- completed the building in 1933. Thomas Boylan designed it to be roughly the size of a giant Diplodocus.
Natural Trap Cave
Bighorn Canyon National Recreation Area – Big Horn County, Wyoming
This site is not accessible, but is interesting. Natural Trap Cave is located on federal public lands managed by the Bureau of Land Management. It is an 80-foot-deep sinkhole-type pit with a 15-foot wide entry. It is nearly impossible to see until it is directly underfoot. This cave became a deadly trap for prehistoric animals. Excavations have revealed fossils buried beneath the sediments here, including mammoth, short-faced bear, collared lemming, lion, cheetah, and camel. Over 30,000 specimens have been collected from the cave over the years, mostly from extinct animals.
Park County, Wyoming
Mummy Cave – located near the eastern entrance to Yellowstone National Park – is an archeological site. Scientists believe that the cave was occupied between 7280 BC and AD 1580.
Rockhounding Sites for Children & Families
Wyoming Fish Fossils
Southwest Wyoming near Fossil Butte National Monument
Near Fossil Butte National Monument, there are several commercial (fee access) businesses that permit fossil collecting. Generally speaking, these fossils occur in quarries where the fossils are recovered from split rock. In 2009, we visited Ulrich’s Quarry. We were able to collect a few fish fossils but then a torrential rain swamped us and the site was closed. This site is located at approximately 7,200 feet above sea level.
Wyoming’s well-known Eocene Blue Forest petrified wood has been collected for generations. Petrified wood occurs at Blue Forest as well as Eden Valley/Woodtop, and Farson/Big Sandy.
Fossils - Pelecypods
South of Kemmerer, Wyoming
Pelecypods occur near Oyster Ridge.
Fossils – Dinosaurs
Commercial (fee access) business. The Wyoming Dinosaur Center sponsors ‘dig for a day’ programs where participants help excavate dinosaur fossils. You do not, of course, get to keep the dinosaur fossils.