Herkimer diamonds are double-terminated quartz crystals discovered within exposed outcrops of dolomite in and around Herkimer County, New York and the Mohawk River Valley. Not actually diamonds, the "diamond" in their name is due to both their clarity and natural faceting - crystals possess double termination points and 18 total faces. Because the first discovery sites were in the village of Middleville and in the city of Little Falls, respectively, the crystal is also known as a Middleville diamond or a Little Falls diamond.
Xystridura Whitehouse, 1936 is a genus of Redlichiid trilobite described originally from the Middle Cambrian (Miaolingian) strata of Queensland, Australia. The genus ranges upwards from Ordian into Florian Stages in terms of Australian Cambrian stratigraphic nomenclature.
The Mount Cap Formation is a geologic formation exposed in the Mackenzie Mountains, northern Canada. It was deposited in a shallow shelf setting in the late Early Cambrian, and contains an array of Burgess Shale-type microfossils that have been recovered by acid maceration.
![Tonto Group Geologic formation in "[[Grand Canyon]] region, United States](https://upload.wikimedia.org/wikipedia/commons/thumb/2/2f/Grand_Canyon-Mather_point.jpg/320px-Grand_Canyon-Mather_point.jpg)
The Tonto Group is a name for an assemblage of related sedimentary strata, collectively known by geologists as a Group, that comprises the basal sequence Paleozoic strata exposed in the sides of the Grand Canyon. As currently defined, the Tonto groups consists of the Sixtymile Formation, Tapeats Sandstone, Bright Angel Shale, Muav Limestone, and Frenchman Mountain Dolostone. Historically, it included only the Tapeats Sandstone, Bright Angel Shale, and Muav Limestone. Because these units are defined by lithology and three of them interfinger and intergrade laterally, they lack the simple layer cake geology as they are typically portrayed as having and geological mapping of them is complicated.
The Jordan Formation is a siliciclastic sedimentary rock unit identified in Illinois, Michigan, Wisconsin, Minnesota, and Iowa. Named for distinctive outcrops in the Minnesota River Valley near the town of Jordan, it extends throughout the Iowa Shelf and eastward over the Wisconsin Arch and Lincoln anticline into the Michigan Basin.
The Oriskany Sandstone is a Middle Devonian age unit of sedimentary rock found in eastern North America. The type locality of the unit is located at Oriskany Falls in New York. The Oriskany Sandstone extends throughout much of the Appalachian Basin.
The Davis Formation is a geologic formation in Indiana and Missouri. It preserves fossils dating back to the Cambrian period.
The Eau Claire Formation is a geologic formation in the north central United States. It preserves trilobite fossils from the Cambrian Period.
The Shady Dolomite is a geologic formation composed of marine sedimentary rocks of early Cambrian age. It outcrops along the eastern margin of the Blue Ridge province in the southeastern United States and can be found in outcrops in the states of Alabama, Georgia, Tennessee, North Carolina, and Virginia. It is also can be found in the subsurface of Kentucky, Ohio, and West Virginia. The Shady is predominantly composed of dolostone and limestone with lesser amounts of mudrock. It contains fossils of trilobites, archaeocyathids, algae, brachiopods, and echinoderms, along with the enigmatic fossil Salterella. The Shady Dolomite was first described by Arthur Keith in 1903 and was named for exposures in the Shady Valley of Johnson County in the state of Tennessee. Near Austinville, Virginia, the Shady hosts ore deposits that have been mined extensively for lead and zinc ore.
The Herkimer Formation is a geologic formation in New York. It preserves fossils dating back to the Silurian period.
The Monkton Quartzite is a geologic formation in Vermont. It preserves fossils dating back to the middle of the Cambrian period.
The Franconia Formation is a geologic formation in the upper mid-western United States, with outcroppings found in Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio, and Wisconsin. It preserves fossils dating back to the Cambrian period. It was named the Franconia Formation due to the first published documentation of exposures in vicinity of Franconia, Minnesota in the 1897 Ph.D. dissertation by Charles P. Berkley at the University of Minnesota titled Geology of the St. Croix Dalles. The Franconian stratigraphic stage was named after this formation.
The Hindsville Formation, or Hindsville Limestone Member of the Batesville Formation, is a geologic unit in northern Arkansas and eastern Oklahoma that dates to the Chesterian Series of the late Mississippian. Named for the town of Hindsville in Madison County, Arkansas, this unit is recognized as a member of the Batesville Formation in Arkansas and a geologic formation in Oklahoma. Although, some workers have proposed raising the rank of this interval in Arkansas to formation status. Both the Batesville and Hindsville Formations overlie the Moorefield Formation and underlie the Fayetteville Shale.
The Bloyd Formation, or Bloyd Shale, is a geologic formation in Arkansas. It preserves fossils dating back to the Carboniferous period.
The Pitkin Formation, or Pitkin Limestone, is a fossiliferous geologic formation in northern Arkansas that dates to the Chesterian Series of the late Mississippian. This formation was first named the "Archimedes Limestone" by David Dale Owen in 1858, but was replaced in 1904. The Pitkin conformably overlies the Fayetteville Shale and unconformably underlies the Pennsylvanian-age Hale Formation. Some workers have considered the top of the Pitkin Formation to be a separate formation called the Imo Formation. However more recently, others have considered it as an informal member of the Pitkin Formation.
The Potosi Formation is a geologic formation in Missouri and Indiana. It preserves fossils dating back to the Cambrian period.
The Deadwood Formation is a geologic formation of the Williston Basin and Western Canada Sedimentary Basin. It is present in parts of North and South Dakota and Montana in the United States, and in parts of Alberta, Saskatchewan, and southwestern corner of Manitoba in Canada. It is of Late Cambrian to Early Ordovician age and was named for exposures in Whitewood Creek near Deadwood, South Dakota. It is a significant aquifer in some areas, and its conglomerates yielded significant quantities of gold in the Black Hills of South Dakota.
The Sawatch Formation is a geologic formation in eastern Colorado. It is a sedimentary sequence formed approximately 530 million years ago during a marine transgression. It preserves fossils dating back to the Cambrian period. It is composed of glauconitic and quartz-rich sandstone.
The Forteau Formation is a geologic formation in Newfoundland and Labrador. It preserves fossils dating back to the Cambrian period.
The Skoki Formation is a stratigraphic unit of Early to Middle Ordovician age that is present on the western edge of the Western Canada Sedimentary Basin in the Canadian Rockies of Alberta and British Columbia. It was named for Skoki Mountain near Lake Louise in Banff National Park by Charles Doolittle Walcott in 1928. The Skoki Formation is fossiliferous and includes remains of brachiopods and other marine invertebrates, as well as conodonts and oncolites.
