Quartz after Calcite (SIL-0014)

specimen number:
9273190

location:
Crystal Cave, Ouray Co., Colorado, USA

description:

A cluster of what were once large scalenohedral crystals of calcite, these now replaced by beautiful sparkling white micro crystals of quartz. This is hollow, the calcite crystals are now gone. This is shown in the video. In super condition all around.

The Crystal Cave, located within the prominent Amphitheater formation of the Uncompahgre mining district near Ouray, Colorado, is a celebrated geologic feature known for producing mineral specimens rather than commercial ore. Geologically, the locality is situated within a region of intense Tertiary-aged volcanism and subsequent hydrothermal activity associated with the Ouray fault system and the San Juan volcanic field. Low-temperature, mineral-rich groundwaters circulating through localized cavities in the sedimentary and volcanic sequences precipitated large scalenohedral calcite crystals, which were later coated by a sugary crust of fine quartz before the underlying calcite dissolved completely away. This process left behind classic, hollow quartz epimorphs after calcite, highly prized by mineral collectors as distinct crystal casts. Because Crystal Cave is a natural solution cavern and localized mineral pocket rather than an industrial corporate mine or quarry, it has no formalized industrial dates of operation, though independent field collectors and mineralogists have actively documented and excavated the site from the late nineteenth century through to the modern era.

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