Freibergite, Tetrahedrite, Chalcopyrite: Eagle Mine, Gilman, Colorado USA

Species: Freibergite, Tetrahedrite, Chalcopyrite

Locality: 20-28 Orebody, NJZC Eagle Mine, Gilman, Eagle County, Colorado USA

Dimensions: 12.5 x 7.5 x 4.5 cm.

This is an excellent large cabinet-size example of silver-rich tetrahedrite (freibergite) on tetrahedrite crystals on a corroded chalcopyrite crystal matrix from the 20-28 Orebody of the Eagle Mine in Gilman, Eagle County, Colorado USA. The Eagle mine was for many years Colorado’s most prolific producer of mineral specimens. Closed since 1984, specimens such as this nice example are now considered classics for Colorado.

This specimen is from the collection of John R. Helms, a mine foreman who worked for the New Jersey Zinc Company at the Eagle mine for over 35 years. Persson Rare Minerals was able to acquire this unique collection of Colorado minerals from the Helms family earlier this fall. Mr. Helms had a passion for minerals and mineral collecting his entire life, and his collection represents a very diverse and complete cross-section of the minerals which are found at this iconic Colorado mining district, which has been long-closed.

This is a fine cabinet-size example of a rare classic from Gilman, in excellent condition as well. The freibergite has been analyzed by SEM-EDX and found to contain enough silver to qualify it as freibergite (which has recently been redefined by the IMA as ‘argentotetrahedrite’). The freibergite-tetrahedrite crystals are up to ~1 cm and quite sharp and well-formed on all surfaces of this 3-dimensional specimen. Annette Slade photo. Classic!