Quartz var. Youngite

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An attractive aesthetic example of crystallized quartz covering a breccia matrix. These are often referred to as youngite. Not terribly common on the market today, brightly fluorescent. The fluorescence is shown at the end of the video.The town of Guernsey, located in Platte County, Wyoming, lies within the geologically complex Hartville Uplift, a region where Paleozoic sedimentary rocks unconformably overlie Precambrian basements. Within the Mississippian-aged Guernsey Limestone, ancient karst caves and fractures became sites of extensive brecciation, where tectonic shifts shattered existing red and peach-colored jasper into angular fragments. Over time, low-temperature, silica-bearing groundwaters circulated through these subterranean cavities, cementing the shattered jasper with layers of translucent chalcedony and capping the structures with a delicate, sparkling crust of grayish, druzy quartz. This highly distinctive, localized material is known as youngite. Historically, the primary source of this material was the Youngite Caves area near Guernsey. These localities have long been closed to collecting because they are situated on private and state-managed lands. In addition to its chaotic, brecciated patterns, youngite is recognized for its strong, neon-green fluorescence under shortwave ultraviolet light, which is caused by trace amounts of uranium incorporated into the silica during its formation.