Ashcroft District
The Ashcroft District was recognized by Vanderwilt (1947) on Castle Creek in the Elk Mountains. The terrain is severe, with the Montezuma Mine standing at 13,000 feet. A large quartz diorite stock intrudes into Paleozoic sediments in the area. There was a lot of interest in magnetite ores in the district, and the Ashcroft is adjacent to the Taylor Peak District of Gunnison County (Harder, 1909). Some gold was found with exploration into lead-silver occurrences, but the district was not much of a producer.
The town of Ashcroft was founded about the same time as Aspen and outpaced its rival for a while (Eberhart, 1969). The Railroad - and richer ore - provided the impetus to make Aspen the more successful town.
Aspen District (aka Roaring Fork District)
Webmaster's note - additional info is available lower in the page in the Roaring Fork District description.
The Aspen District was considered by Vanderwilt (1947) to contain - or to be synonymous with - the Roaring Fork, Richmond Hill, and Lenado Districts. In any case, the principle mines of the district lie within a mile of the town of Aspen. The District was a leading producer of silver, along with some lead and zinc, and minor gold. There was not much pyrite present in the ore, the major gangue minerals being barite and dolomite. Most production occurred from stratabound ores in the Leadville Limestone and Dolomite and the overlying Weber Shale.
The first prospectors arrived in the area in the 1870s, but the fear of Indian attack drove them back to the comparative civilization of Leadville. Finally in 1880, rich ore was struck and mining progressed, inhibited somewhat by poor access. A road over Independence Pass spurred growth, but the coming of the railroad in 1887 was the big event. Aspen was considered in 1893 the richest silver town in the world and was second only to Leadville in production (estimated by Vanderwilt at over $105M by 1947).
The biggest producer in the Aspen District was the Smuggler Mine. To highlight its status, the mine produced the largest silver nugget in history - a 2054 pound beauty with 93% purity.
Additional references for this District include: Bryant (1971, 1979), Emmons (1888), Freeman (1972), Rohlfing (1938), Spurr (1898, 1909), and Vanderwilt (1935).
Avalanche District
Discussed in Vanderwilt (1947), the Avalanche District lies around Avalanche Creek several miles upstream from the Crystal River. Argentiferous galena and some gold is found in limestone beds near the Mount Sopris intrusion. Vanderwilt points out that production was minor.
According to Eberhart (1969), gold was found in 1880 and a number of claims were staked on Avalanche Creek. The town of Janeway at the mouth of Avalanche Creek supported the area and about 100 residents.
Castle Creek District (aka Columbia District)
The location of the Castle Creek District is confusing. Henderson (1926) considers it synonymous with the Columbia District. Dunn (2003) describes the district as lying in two parts separated by the Columbia District. Refer to the Columbia District for lists of minerals and mines.
Columbia District
Henderson (1926) identifies the Columbia District as synonymous with the Castle District, the West Castle District, and the Roaring Fork District. Dunn (2003) considered the Columbia District to overlap or include the Castle and West Castle Districts. On mindat.org, the district is considered synonymous with the Ashcroft District.
Despite the mineral list below (mindat.org), the district was mainly an iron producer. Eberhart (1969) describes the small settlement of Cooper's Camp that rose to serve the small mining community.
Difficult District (aka Difficult Creek District)
The Difficult District was identified by Henderson (1926) as lying in the southeast corner of Pitkin County near the Gunnison County line. Ore deposition is probably associated with the Difficult Creek Quartz Monzonite (Bryant, 1979). BLM mineral surveys of the area identified gold and copper with minor silver in vein deposits. The district now lies within the Collegiate Peaks Wilderness Area.
Frying Pan District (aka Dry Pine District)
The Frying Pan District was noted by Henderson (1926) and again by Vanderwilt (1947). Vanderwilt describes small scattered veins throughout a large area around Nast, a station on the Colorado Midland Railroad. Vanderwilt defines the district as stretching from the head of Homestake Creek in Eagle County, along Frying Pan Creek and to the head of the Lake Fork of the Arkansas River in Lake County. He notes that gold and silver occur in these veins in Precambrian granite.
Several of the mines listed on mindat.org (and the associated minerals) are uranium minerals, associated with small uranium deposits (Nelson-Moore et al., 1978).
Highland District
Just south of the town of Aspen, the Highland District lies between the Aspen District and the Ashcroft District (Henderson, 1926). Prospectors made some finds in 1879 and established the town of Highland, but the boom didn't last long (Eberhart, 1969). Activity peaked in about 1881, and continued intermittently to 1890 (Dunn, 2003). Another reference for this district is Spurr (1898).
Hunter Creek District
Henderson (1926) listed the Hunter Creek District in his compilation of Colorado mining districts, and named it as synonymous with the Woody District. It is enclosed in the larger Aspen District, lying along Hunter Creek, which flows into Aspen from the East. No specific information is available on the Hunter Creek district. Refer to Aspen District.
Independence District
The Independence District is a minor district of large extent in the area of Independence Pass south of Aspen. Mindat.org includes the Independence District with the Columbia District, which seems quite a stretch. Including the headwaters of the Roaring Fork River, the district produced some very rich gold ore. Vanderwilt (1947) quotes stopes yielding 2.3 ounces per ton of gold in 1932, but production diminishing to 2 tons in 1940. In fact Dunn (2003) indicates that most of Pitkin County's gold production probably came from this district. Silver was also present.
Mindat.org lists several other mines in the area of Independence Pass. One is the Grotto Pegmatite Mine; another is the Pitkin Mine, apparently a producer of iron ore. The Independence Mine - included by Dunn (2003) in the Independence District and by mindat.org in the Lincoln District, contained chalcopyrite, gold, and silver.
The town of Independence was the first settlement in the Aspen area, lying below the summit of the pass on the west side. It was also known, from time to time, as Chipeta, Sparkill, or Farwell (Eberhart, 1969).
The Independence District now lies largely within the Collegiate Peaks and the Hunter-Frying Pan Wilderness Areas.
Lenado District (within Aspen District)
Lenado has been generally considered as part of the larger Aspen District or Roaring Fork District (Dunn, 2003; Vanderwilt, 1947). Bryant (1978) mentions the Lenado District as a "satellite" district of the Aspen District.
The geology of the Lenado District is basically the same as the Aspen District. The Lenado Project discussed by Bryant (Ibid) provided some 1370 feet of diamond drilling in the Woody Creek valley with an accompanying geochemical study by McCarthy and Gott (1966). The drill core (albeit with poor recovery) revealed numerous faults and breccias that Bryant and other investigators interpret to a paleokarst origin - collapse of the active erosion surface by dissolution of underlying carbonates.
Spurr's landmark paper (1898) contains a small section on the Lenado Canyon area (pages 117-125.) Spurr delineates the stratigraphy as a shale overlying a carbonate overlying a Cambrian quartzite. At the Aspen Contact Mine, Spurr reports that the dolomite is "much broken up" with blocks of limestone and ore. He describes a breccia between the dolomite and the underlying quartzite referred to by the miners as "talc," where the richest ores occur. Those zones are significant - up to 40 feet thick stretching up to 300 feet laterally. (This description can certainly fit with Bryant's paleokarst explanation.)
The Leadville Mine shows the same geology as the Aspen Contact Mine. The ore is mainly lead and zinc sulfide with some carbonate (Spurr, Ibid).
Eberhart (1969) describes the town of Lenado as a small settlement in the midst of the best mines in the canyon. It became the home of the area's largest employer - the Varney Tunnel Company. A large lead mill opened in the town in the early 1890s and closed and opened several times. The last production was in 1917 to provide zinc to the war effort (Eberhart, Ibid).
Lincoln Gulch District (aka Lincoln District; aka Ruby District)
Vanderwilt (1947) describes the Lincoln Gulch District as lying 15 miles southeast of Aspen, where Lincoln Gulch runs into the Roaring Fork River. The district abuts the Red Mountain District of Chaffee County on the south, with Red Mountain dividing the two.
Vanderwilt (Ibid) describes the northern part of the District as containing pyritized iron-stained rock with stringers of galena and sphalerite and scattered molybdenite flakes. The southern part of the area consists of granite and schist with small veins containing lead and silver and small rich lenses of auriferous chalcopyrite. He notes that in 1938 and 1939 six tons of ore were shipped averaging 15 percent lead, 8 ounces per ton silver, and 0.7 ounces per ton gold.
Worcester (1919) mentions the Greenhorn Occurrence in his compilation of molybdenum occurrences in Colorado.
The town of Ruby was founded in Lincoln Gulch in the 1890s. The mines were not big producers and have not operated since World War I (Eberhart, 1969).
Much of the District now lies within the Collegiate Peaks Wilderness area. The geology and resources of the wilderness area is covered in detail by Bastin (1987) and additional information can be obtained from a thesis by Cruson (1973).
Maroon District
The Maroon District was listed by Henderson (1926). Not much information is available, except for Bryant (1969) who lists a placer gold occurrence (the Continental Placer). Includes the West Maroon District, for which no information is available.
Woody Creek District (aka Woody District)
The Woody Creek District, named by Henderson (1926), lies along Woody Creek north of the town of Aspen, adjacent to the Lenado District. It is included within the Aspen District. According to Dunn (2003), the Woody Creek District adjoins and may overlap the Hunter Creek District. Additional references include Bryant (1972) and Freeman (1972).
Richmond Hill District
Nestled in among the Highland, Castle Creek, and Columbia Districts, the Richmond Hill District lies just south of the town of Aspen and the Aspen ski area. Considered by Vanderwilt (1947) as synonymous with the Aspen District, a more detailed description can be found under that district.
Roaring Fork District
Generally considered synonymous with the Aspen District (Dunn, 2003; Vanderwilt, 1947), the Roaring Fork District is named for the river of that name. Nearly all the significant mines were within a mile of the town of Aspen. The Roaring Fork/Aspen District was famous for its silver production, with over $100M attributed by Vanderwilt (Ibid).
The geology of the area consists of Paleozoic sedimentary rocks (striking North to Northeast, dipping west) lying on Precambrian granite and schist with intrusions of Laramide age bringing ore-bearing solutions. The Castle Creek Fault, west of the town of Aspen, is the major structural feature of the district, bisecting the Aspen area. Spurr (1898) accounted 5000 feet of displacement west of the town, while Bryant (1979), attributing a better knowledge of the Maroon Formation, calculated some 14000 feet of displacement at Aspen Mountain, bringing the Precambrian rocks against the upper portion of the Maroon Formation. Spurr (Ibid) and Freeman (1972) had somewhat different interpretations.
As in so many Colorado mining districts, the Leadville Formation is the focus of the mineralization. Spurr (Ibid) defined the Leadville as containing the Dyer Dolomite, the Gilman Sandstone and the Leadville Limestone. Above the Leadville, the Weber Shale (of Spurr) - the Belden Shale (of Bryant) - was deposited and is the focus of ore deposition. Disagreement has existed about whether the mineralization at the Leadville - Belden contact and the limestone-dolomite contact was along bedding plane faults or if the zone was just a depositional contact. Bryant took particular note of features that imply cavities and brecciation were present as a result of karst development during a period of erosion between deposition of the Leadville and the overlying Belden and that some ore deposition occurred in the breccias and in cavities. Bryant (1979 - page 106) presents an extensive list of references about these competing interpretations.
Rock Creek District
The Rock Creek District was listed by Henderson (1926). He placed it in far western Pitkin County, currently within the Maroon Bells Wilderness Area. No information could be located about this district.
Snowmass District
The location of the Snowmass District is not well defined. Henderson (1926) describes it as four sections in T10S, R85W, placing it on the lower reaches of Snowmass Creek near the present location of the Buttermilk ski area and Snowmass Village. Vanderwilt (1947), on the other hand, describes the district as consisting of prospects near the head of Snowmass Creek, a location more than six miles southwest of Henderson's. Further, there are old prospects on the west side of Snowmass Village that don't fit either location.
Prospects and mines also appear within the Highland Peak Quadrangle (Bryant, 1972) and the Woody Creek Quadrangle (Freeman, 1972). For these reasons, the map associated with this description shows the tentative Snowmass District as including a very large area, encompassing all those above. While the lower reaches of Snowmass Creek lie around the developed areas noted above, the headwaters are within the Maroon Bells - Snowmass Wilderness Area.
Vanderwilt (1947) described the deposits as associated with a quartz monzonite stock that makes up Hagerman Peak and Capital Peak. Small veins occur with lead, zinc and copper. He reports no production, although some production is indicated on mindat.org for the district.
Spring Butte District
The Spring Butte District is listed by Henderson (1926) as a small (three sections) district in the northwestern part of Pitkin County. It may abut the Avalanche District and is considered the same as the Avalanche District on mindat.org. Refer to the Avalanche District for more information.
West Castle Creek District (aka West Castle District)
The West Castle Creek District appears in Henderson (1926), but no further information is available.
West Maroon District
The West Maroon District is included in Henderson (1926) as encompassing eight sections in the southern part of T11S, R86W, in the area of Maroon Pass and Maroon Peak. The district lies within the Maroon Bells - Snowmass Wilderness area.
