Elk Creek, Meade County, South Dakota, USAi

Regional Level Types
Elk Creek	Creek
Meade County	County
South Dakota	State
USA	Country

Habit: elongate parallel to <010>…Length to width ratios vary between to 2 to 1 and 7 to 1, resulting in stubby to elongate prismatic crystals

Colour: colorless, yellow, amber or deep golden brown, transparent crystals

Description: Roberts and Rapp also noted that the dome faces on some crystals are curved right, left, backwards and forwards. These faces may also be rather bumpy and upon close inspection these “bumps” actually represent numerous growth hillocks which may indicate stress within the crystal structure. Th is supported by the extreme sensitivity these crystals have to abrupt temperature changes (e.g., handling a cool crystal with warm fingers); the crystal will immediately fracture internally. Nevertheless, Sinkankas (1959 reports that Elk Creek barite has been more successfully cut and faceted than barite from other localities because the crystals are far less inclined to split. Barite from this locality fluoresces and phosphoresces bright yellow-white under shortwave ultraviolet radiation…”1 “At the Elk Creek and Hoover localities barite occurs in fossiliferous, septarian, calcareous concretions. Concretions are found in several units of the Pierre shale, but at the Elk Creek locality the barite-baring concretions are found within the Gregory Member. This stratigraphic unit is characterized by the presence of Baculites gregoriensis. It is not known with certainty whether the unit hosting the barite-bearing concretions at Hoover is the Gregory Member or not. Along Elk Creek, limestone concretions are found in at least four distinct horizons. Generally, the best horizon is the lowermost one that occurs at or near the creek bottom. Since the bedding is essentially horizontal this lower horizon can be traced for some distance within the draws. Potential barite-bearing concretions can be characterized and oblate spheroids 1 to 3 meters in maximum dimension; they are septarian, fossiliferous and partially hollow. Septa are composed of yellow calcite. Invertebrate fossils found in the concretions include the Cephalopods