8.4" Polished Wyoming Youngite Agate/Jasper Slab - Fluorescent

This is a 8.4" wide polished slab of Youngite that was collected from the Youngite Caves near Guernsey in Platte County, Wyoming. Youngite is a brecciated jasper that is often found encrusted in chalcedony. Under short wave UV, this agate fluoresces vibrant green.

Jasper is a term that can be applied to an opaque variety of chalcedony (light does not pass through it) The opaqueness is due to a much larger amount of impurities mixed with silica/quartz. Like agate it may form in a huge variety of colors, and is often multi-colored. In most cases, jasper will occur when silica-rich fluids permeate throughout a soft sediment or volcanic debris deposit. The fluids then crystallize around the particles/impurities, resulting in a cementation process. Most often, the impurities present determine the coloration of the deposit following solidification, however other factors can play a role in the color of what is now considered a jasper.

Agate is a variety of microcrystalline quartz (chalcedony) that displays translucence and in some cases banding. Agate primarily forms when silica-rich fluids fill pockets within rock and/or fossils, resulting in deposition of the silica along the walls of the rock. This process can result in banding patterns as the composition and impurities of the fluids change over time. These banding patterns can either form as flat layers or rounded layers, depending on the surfaces available for deposition.

The term "brecciated" is related to a previously solid rock that has undergone pressures and shifting that caused broken-up, angular fragments. Following the breaking of this rock, ground water containing silica assisted in the natural cementing process of the fragmented rock, resulting in this beautiful mineral formation.

Chalcedony var. Jasper/Agate
Youngite Caves, Guernsey, Platte County, Wyoming
8.4 x 6.8", up to .58" thick