Calcite on Sphalerite

Cumberland Mine, Smith County, Tennessee, USA

19 x 26 x 11.5 cm (7½ x 10¼ x 4½ inches). 5.05 kilograms (11.13 pounds).

This commanding calcite specimen originates from the Cumberland Mine, located in Carthage in Smith County, Tennessee. It represents a rare convergence of scale, preservation, and crystallographic form. Measuring 26 centimeters across at its widest point, the primary scalenohedral crystal is unusually large for the region, and even more unusually, it is fully intact, complete on all sides without cleavages or contact marks. While large calcite crystals are known from this district, they are seldom preserved in fine condition. This example is a notable exception.

The crystal exhibits the classic scalenohedral habit characteristic of both the Cumberland and Elmwood Mines (both located in Tennessee), with well-defined geometry and a distinct twinning, as is frequently observed from this locality. The faces are vitreous and mirror-like, sharply lustrous and reflective, while the internal body has a warm, saturated amber-orange coloring. Thanks to its translucence, light imbues this crystal with an ephemeral glow. The calcite is anchored on a contrasting matrix of lustrous sphalerite, a pairing characteristic of the deposit. The contrast between the brilliant orange crystal and the dark sphalerite matrix adds not only visual impact, but geologic significance, illustrating the mineral paragenesis of the deposit.

Geologically, the Cumberland Mine is a Zn–Pb–Cd–Ba (baryte)–dolomite system. The host rocks were deposited approximately 470 million years ago, and mineralization followed much later, emplaced through hydrothermal activity into fractured and brecciated zones at depths of approximately 334 to 360 meters.

This specimen comes from the well-known collection of Dr. Steve Neely, a devoted regional collector whose proximity to the mine and focused eye for quality led him to assemble one of the most important suites of Cumberland calcites. This particular piece stands out not only for its great size, but its sculpturesque form and outstanding quality. It is a rare survivor from one of the most productive yet unforgiving working mines in North America.

Source: https://www.sothebys.com/en/buy/auction/2025/natural-history-2/calcite-on-sphalerite