Sphalerite with Quartz

specimen number:
2063534

location:
Patch Glory Hole, Central City, Gilpin Co., Colorado, USA

description:
A grouping of sharp twinned to sphalerite crystals 1.2 cm in size on matrix with crystallized quartz and what appears to be small crystals of calcite. Minor pyrite is also present. Collected by Ray DeMark on July 5, 1986. The prominent crystal is in good condition, there is a set of small cleaved crystals on the far right end of the matrix.

Located on Quartz Hill southwest of Central City in Gilpin County, Colorado, the Patch Glory Hole represents a major feature within the historically famous region nicknamed the Richest Square Mile on Earth. Geologically, the deposit consists of an oval-shaped vertical breccia pipe plunging steeply downward through Precambrian metamorphic rocks. Mining in the Central City district began following the 1859 gold rush, and extensive underground workings later intersected this fractured breccia zone. Continued excavation and selective cave-in techniques eventually caused the surface above the underground stopes to collapse, forming an enormous open pit or glory hole measuring roughly 1100 feet long by 800 feet wide. Mineralization within the fractured zone dispersed ore into stockworks, rich in quartz gangue and various sulfides like pyrite, chalcopyrite, sphalerite, and galena, accompanied by notable native gold. Consolidation of the property by Dr. Muchow in the 1920s sustained significant gold production through the Great Depression era. Modern interest in the area remains strong among historic preservationists and mineral collectors, though steep pit walls, unstable rock faces, and private property boundaries strictly limit physical access to the site.

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