Colorado’s Silver Thread Scenic Byway (CO 149) was the route of the all-day field trip to the Anaconda Mine site in the Gunnison Gold Belt, Powderhorn, Lake City, Henson Creek and the Ute-Ulay Mine, and Lake San Cristobal.

The Gunnison Gold Belt lies about 15 miles south of Gunnison and is about 25 miles long trending roughly SW-NE. It was discovered in 1894 and several small mining camps were quickly established.  Most were short-lived.  The largest mine was the Vulcan which operated until 1906.  The deposits here high in sulfides, in fact, sulfur was a product at some locations. The tour stoped briefly at the reclaimed Anaconda Mine site.

The Powderhorn Mining District (AKA the White Earth Mining District) is the site of the Iron Hill composite stock, an extensively explored portion of the rare metal-rich White Earth Complex that contains thorium, titanium, selenium, barium, and niobium.  Thorium has been found in 33 separate deposits, primarily in NW-trending, mineralized shear zones in foliated pre-Cambrian rocks, in a 6 mile-wide, 20-mile-long area.  However, the only mining in the area was for gold and silver on either side of Nine-Mile Hill at Spencer, Midway, and Vulcan during the late 19th century.

The nearly circular, volcanic Lake City Caldera lies southwest of the Hinsdale County seat, Lake City.  Henson Creek bounds the caldera to the north and the Lake Fork of the Gunnison River bounds the east and south.  Gold and silver were first discovered in the district in 1871 at the Ute-Ulay claim.  Despite the region remaining part of the Ute Tribe reservation, prospectors rushed into the Lake Fork valley to stake claims.  By the time that Alfred Packer’s party arrived in 1874, Lake City had been established at the confluence of the Lake Fork and Henson Creek as the primary settlement in the region.  Difficult transportation access made shipping equipment and milled ore very expensive until the Lake City branch of the 3’-gauge D&RG railroad finally arrived in 1889.  However, only 3 years later, silver prices crashed and silver mining throughout Colorado took a nose-dive.  The Ute-Ulay silver-lead mine was one of the longest-lasting mines on Henson Creek. Limited precious metal mining continued sporadically in Hinsdale County until the 1960s, but never recovered to its 1880’s peak. 

Another mine, the rich Golden Fleece, produced gold tellurides from a shaft high above Lake San Cristobal, several miles south of Lake City.  By 1945, Hinsdale County mines had produced more than 67,000 ounces of gold and 5,000,000 ounces of silver, plus copper, lead, and zinc, worth more than $400 million at 2024 prices.

(Adapted from the original written by Steve Hart, 2025)

STOP 1 on the Lake City Tour was at the Anaconda Mine site, one of the histoic mines in the Gunnison Gold Belt.

(Above) Geologist, Allen Stork, describes the geologic formations in the Gunnison Gold Belt which is about 25 miles long and lies about 15 miles south of Gunnison. The tour stop was at the Annaconda Mine site which has been reclaimed by the Bureau of Land Management (BLM). The filled shaft is the mound in the foreground.  All buildings have been removed.   CLICK HERE for a map of the locations of Gold Belt mines from USGS Bulletin 1550.

(Right) The upper 5 specimens (from the mine dump) are Precambrian rocks showing green traces of copper mineralization.  The lower 2 specimens are massive sulpfide minerals, mainly pyrite.

Tools used in a Wood Shop and by timbermen underground.

(Above) Allen Stork’s tour handouts show the overall geology of the Gunnison Gold Belt (Left) and a closeup of the Anaconda Mine area (Right).  CLICK HERE for a more detailled map of the Anaconda Mine site.

STOP 2 was near one-time small settlement of Powderhorn and the Mining District of the same name (AKA the White Earth Mining District).  Iron Hill, at the center of the district, is a composite stock that has been extensively explored.  The White Earth Complex contains carbonatite rocks containing rare-earth elements such as thorium and niobium, plus titanium, selenium, and barium.  Rare-earth minerals are actively being sought Worldwide because of their unusual properties used in magnets, electronics, and metallurgy.  The Mountain Pass, California deposit is currently the most important domestic source for rare-earths.  Concentrates from Mountain Pass must be shipped to China for refining because there is no US refinery.

The Powderhorn area is beautiful ranching country.

Allen Stork explains the complex geology in the Powderhorn area.  The map is shown below.

Carbonatites are unusual igneous rocks because they are composed of carbonate minerals like calcite or dolomite rather than the usual silicate minerals.  The MHAer is comparing a carbonatite specimen with the geologic map.

Allen Stork’s geologic map shows Iron Hill near the center.  CLICK HERE for an enlarged sketch of the Iron Hill area.

Carbonatite dikes are visible in the road cut.

STOP 3 was a lunch break in Lake City and an opportunuty to learn more about the unique geologic features of the San Juan Mountains and to visit the Hinsdale Historical Society Museum before embarking for the Ute-Ulay Mine in the Henson Creek Valley. 

The topographic model shows several creeks that follow the edges of some of the calderas.

(Above) Harvey DuChene describes the several calderas in The San Juan Mountains.

Joe Fox welcomes the MHAers to Lake City and to the Lake City Historical Society Museum.

The museum occupies the historic Finley Block which was built in 1877 by Henry Finley one of the early Lake City founders, entrepreneurs, and mine owners.  It was initially occupied by Schiffer and Company, a mercantile establishment. In subsequent years it was used by other businesses and was the Odd Fellows Lodge until the late1940s.

(Left) Banner from the Silver Star Lodge No. 27 of the Independent Order of Odd Fellows.

(Above) While certainly not a “favorite son,” Alfred Packer may have been the most notarious Lake City resident. Convicted of murder and canibalism, his hanging would have been a major event in the town.  Tickets were required.  Ultimately he escaped the noose. His sentenace for murder and canibalism was later commuted after he had spent many years in prison.