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Geological Survey Bulletin 707
Guidebook of the Western United States: Part E. The Denver & Rio Grande Western Route |
ONE-DAY TRIPS FROM DENVER.
(continued)
GEORGETOWN AND MOUNT McCLELLAN.
The journey to Georgetown is made on a narrow-gage line of the Colorado & Southern Railway and is confined entirely to the valley of Clear Creek, which joins South Platte River about 6 miles north of the Union Station in Denver. From Denver to Golden the general course of the road is up the broad, flat valley, which is irrigated by water taken from the creek higher up. This valley is highly cultivated, and many fields of grain (see Pl. III, A, p. 7) may be seen from the train. Near the mountains the bottom of the valley is composed largely of gravel and boulders brought down by the creek in times of flood, and crops grown on such soil are scanty even where water for irrigation is abundant.
Just below Golden (named in honor of Tom Golden, one of the pioneers of this region) the valley narrows and is flanked on either side by flat-topped hills, or mesas,4 as they are generally called in the Southwest, about 400 feet high. These mesas are remnants of a once extensive plain formed at this level by streams that planed off the inequalities of the land. Where the beds of rock are horizontal, as they are about Denver, the surface of the plain corresponds to the bedding of the rocks, but where the rocks are upturned on the flank of the mountain, as they are at Golden, they were planed off just the same. After the streams had reduced the soft rocks to a relatively smooth surface a great flood of lava that was ejected from some vent in the mountains rolled out over the plain and spread for a distance of many miles. When this mass of lava cooled and became consolidated it formed a rock called basalt, which is harder than the soft sandstone and shale upon which it rests, and for that reason it served as a protecting cap when the region was uplifted and streams began to cut the rocks away. Most of the basalt is now gone, and the parts seen from the train are doubtless mere fragments of a once extensive and continuous sheet. The rocks upon which the lava was spread are the Denver and Arapahoe formations, of Tertiary age, and the Laramie formation, of Cretaceous age.
4Flat-topped hills are named mesas because of their resemblance to a table (Spanish mesa, pronounced may'sa).
Behind these mesas, which, are outliers or foothills of the mountains, is a beautiful valley, which has been eroded in the upturned edges of the softer and lower formations. These rocks can not be seen distinctly from the train, but in near-by localities they are well exposed as they bend upward and rest upon the granite that forms the mountain mass. In this valley is Golden, which for a time was the Territorial capital. Here is the Colorado School of Mines, some of the buildings of which may be seen on the left. Here are also smelters and mills for reducing the ores mined farther up the creek.
Immediately on leaving Golden the train plunges into the narrow, tortuous canyon which Clear Creek has cut into the uplifted granite mass. When boarding the train at Denver the traveler may have wondered why this road was ever built narrow gage (3 feet), or, even if so built, why it was not changed years ago to the standard gage, but when he sees this canyon he no longer questions the wisdom of the builders of the road in adopting the narrow gage nor that of the management in retaining it. He soon realizes that only a single narrow-gage line could have turned and twisted its way through the canyon and that the change to standard gage would mean the building of extensive tunnels and many bridges. The little narrow-gage line, on the contrary, as shown in Plates VI and VII, winds around every bend of the creek and every projecting spur of the mountain and required almost no cutting of the solid rock.
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| PLATE VI. "MOTHER GRUNDY." "Mother Grundy" from her position overlooking Clear Creek keeps a sharp lookout on all travelers. The massive granite and the tortuous stream are well shown in this picture. Photograph by L. C. McClure. Denver; furnished by the Colorado & Southern Railway. |
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| PLATE VII. NARROWS OF CLEAR CREEK CANYON. In places the gorge is so narrow and the bends are so abrupt that both the stream and the railroad seem to disappear in some rocky cavern, but on rounding the bend they may be seen pursuing their tortuous course hemmed in by vertical or overhanging cliffs several hundred feet high. Photograph by L. C. McClure, Denver; furnished by the Colorado & Southern Railway. |
Although the canyon nearly everywhere has precipitous walls, it varies greatly in width. At some places, as shown in Plate VII, it is merely a cleft sufficient to accommodate the stream that carved it; at others it is so broad that the stream has built flood plains upon which the railroad has little difficulty in finding its way. The cutting power of the stream has been nearly uniform throughout, but the resultant form of the canyon depends largely upon the resisting power of the rock through which it has been cut. Thus, where the granite is exceedingly massive—that is, without joints or fissures of any kind to weaken its resistance—the stream has not greatly widened its gorge, but where the rocks are seamed with innumerable joints, or where they have been so much squeezed as to form schists, the stream has cut out a wide canyon.
The rock in which the canyon is cut is generally called granite, but some of it is banded and is properly called gneiss. (See footnote on pp. 9-10.) The bands of the gneiss show great contortions, which are the result of movements in the rocky crust of the earth. The gneiss is also seamed with dikes (rocky material that was once melted in the earth's interior and forced into fissures of the rock) and veins (mineral matter deposited from waters circulating through fissures in the rock) of great variety of color and texture. In places the rocks are nearly black with the mineral called hornblende; in other places they are composed largely of white or pink feldspar or are gray granites.
At Forks Creek the canyon divides, and the railroad branch to the right runs to Central City and Blackhawk, two of the most important and oldest gold-mining centers of Colorado. Central City was built near the spot where, in 1859, John H. Gregory made the second great discovery of gold in this region.5
5This discovery is described as follows by E. S. Bastin:
In romantic interest and as a record of human achievement in the face of great difficulties the story of the discovery and early development of the mineral wealth of this region can hardly be surpassed by any other chapter in the history of the "winning of the West." A decade after the historic "rush" of the forty-niners to California a second great westward movement of gold seekers from the Eastern States was started by the discovery of gold in alluring quantities near the present sites of Idaho Springs and Central City. It was first found in gravel on the outskirts of the town of Idaho Springs by George A. Jackson, early in 1859. A few months later the rich outcroppings of a gold vein were discovered on the present site of Central City by John H. Gregory. These two discoveries precipitated a stampede of prospectors, and within a few weeks many of the richer veins of the region had been discovered and many new deposits of gold-bearing gravel located. This discovery began an era of mining development that led to the foundation and early growth of Denver and of the State of Colorado. Up to the end of the year 1918 there had been added to the world's supply of the precious metal from the counties of Gilpin and Clear Creek alone approximately $175,000,000. Although the period of maximum production was between the years 1870 and 1900, the two counties still produce annually metals to the value of more than $1,000,000.
The gold-bearing gravel was small in quantity and was worked out mainly in the early years of mining. Since then the gold has been taken mainly from veins. Most of the veins are steeply inclined and traverse schist, gneiss, and granite, with which are associated dikes and irregular masses of younger intrusive rocks—the "porphyries" of the miners. The deepest workings are those of the California mine at Central City, whose shaft descends 2,250 feet down a steeply inclined vein. A few of the veins are traceable on the surface continuously for more than a mile, and most of them are between 1 and 5 feet wide. The principal metals won from the ores are gold and silver, but copper, lead, and recently zinc have also been obtained. From a few of the veins near Central City pitchblende or uraninite, one of the minerals from which radium is obtained, has been mined, and this is the only locality in the United States and one of the few in the world at which the mineral is found in commercial quantities.
The ores are believed by geologists to have been deposited by hot solutions given off from buried masses of slowly cooling "porphyry." The hot waters at Idaho Springs have possibly a similar origin, though their mineral content is probably much less than that of the waters which originally brought up the gold and silver from lower levels.
(See Spurr, J. E., and Garrey, G. H., Economic geology of the Georgetown quadrangle, Colo.: U. S. Geol. Survey Prof. Paper 63, 1908; Bastin, E. S., and Hill, J. M., Economic geology of Gilpin County and adjacent parts of Clear Creek and Boulder counties, Colo.: U. S. Geol. Survey Prof. Paper 94, 1917.)
A few miles above Forks Creek the canyon becomes less rugged. The first level bottom land the traveler has seen since leaving Golden is occupied by the town of Idaho Springs (altitude 7,556 feet), which is noted both as a pleasure resort and as a mining center. The waters are mild solutions of carbonate and sulphate of soda and have temperatures ranging from 75° to 120° F. Hotels and bathhouses make the place very attractive to the traveler who can spend a few days in the bracing atmosphere of this mountain resort.
The first really noteworthy discovery of gold in Colorado is commemorated by a monument at the mouth of Chicago Gulch, a canyon entering that of Clear Creek from the left of the railroad nearly opposite the station at Idaho Springs. This discovery was made by George A. Jackson in January, 1859. When winter was over Jackson returned to the mountains and on May 7 began placer mining on Jackson Bar.
One of the most notable achievements of mining engineering in this region is the Argo (formerly Newhouse) tunnel, whose large waste dumps may be seen in the eastern part of Idaho Springs. This tunnel extends northward for 5 miles to a point beneath the town of Central City. It cuts many of the veins far below the surface, draining the upper workings and facilitating deep mining. Much ore is brought from the Central City district to Idaho Springs through this tunnel, and mining at or below its level has shown that rich gold ore persists in many of the veins at very great depths.
In the vicinity of Idaho Springs the canyon, although wider than it is in the neighborhood of Forks Creek, is still narrow and the walls are studded with jagged or loose rock as they were left by the cutting of the stream and the action of the weather, but from a point a few miles above the town to the crest of the range the canyon bottoms are broad and the slopes are generally smooth and round, so that a cross section of the valley resembles in shape the letter U. This form of valley (shown in fig. 4, p. 11) is due to the scouring action of a glacier that originated near the summit of the range and flowed down the canyon to a point where the ice melted faster than it was supplied from above and where the forward movement of the glacier consequently stopped. Although all this happened ages and ages ago, the surface features above and below this point still present a striking contrast, for the work of the glacier has not yet been obliterated by weathering. The end of the glacier, which was only a few miles above Idaho Springs, is also marked by a moraine—a great accumulation of rounded and scratched boulders that were brought down by the ice and dumped at its lower end.
Both active and abandoned mines and many prospects may be seen on almost every slope of the canyon wall above Idaho Springs. In Gilpin and Clear Creek counties, as in most old mining regions, only a small proportion of the mines are in operation at any one time. Some of those that are not operated are "dead "—that is, their ore bodies have been entirely worked out—but many are idle only temporarily because of inefficient management or insufficient funds with which to make further explorations for new ore bodies. Few veins are rich through their entire extent, and one company may exhaust its resources in exploring lean parts and its successor may continue the exploration for only a short distance and strike rich ore.
A number of the mines that are now idle, especially those near Lawson, Empire Station, Georgetown, and Silver Plume, were worked mainly for silver and have produced fabulously rich ore. Its unusual richness was caused by a process termed "downward enrichment," by which the silver in the upper parts of the veins was dissolved by surface waters and redeposited farther down in the earth. The ores so enriched do not persist to great depths, and on their exhaustion the mines working them are forced to shut down, for the unenriched ore below is too lean to be mined at a profit.
At Georgetown the train begins to climb the well-known "Loop" by which the railroad loops back over itself in ascending the steep mountain side. Above the Loop lies Silver Plume, shown in Plate VIII, which has been one of the most active mining camps in the State. It is reported that more than $29,000,000 in silver has been taken from the mountain north of the town.6
6According to Bastin, the discovery of a gold-bearing vein near the present site of Central City by J. H. Gregory in 1859 stimulated prospecting throughout the drainage basin of Clear Creek, and many such veins were discovered. One of the most productive of these veins was discovered by George Griffith in the vicinity of Elizabethtown (now Georgetown) on August 1, 1859. In 1860 there was considerable excitement around Empire, but most of it was due to the discovery of rich placer gravel. The first valuable deposit of silver ore discovered (in September, 1864) was the Belmont lode, in Mount McClellan. Thus, as early as 1864 all the territory that the traveler will see on his trip to Mount McClellan was prospected in a crude way and to a certain extent developed. The development of mines, however, was greatly handicapped by the lack of means of transportation, both for bringing in supplies and for sending out the products of the mines. This lack was supplied to a great extent in 1870 by the building of what is known as the Georgetown branch of the Colorado & Southern Railway from Denver to Golden, but it was not until 1877 that this line reached Georgetown, and it was several years later before it reached Silver Plume.
Clear Creek County, of which Georgetown is the county seat, reached the peak of its metal production in 1894, since which time its output has been steadily declining until in 1914 it was worth only $884,615. In the next year the district began to feel the effect of the European war, and the value of its output of metals jumped to $1,124,225. In 1917 its metal output was valued at $1,631,219, In 1918 at $1,126,440, in 1919 at $644,882, and in 1920 at $526,369.
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| PLATE VIII. SILVER PLUME. The once flourishing mining camp of Silver Plume lies in a deep canyon that heads in the Continental Divide. The mountain on the right is said to have yielded more than $29,000,000 in silver. The grade up the canyon is so steep that the narrow-guage road must loop back in places over itself to reach the camp. The railroad to Mount McClellan formerly zigzagged up the slope on the left. Photograph by L. C. McClure, Denver; furnished by the Colorado & Southern Railway. |
The traveler's interest in the things he sees above Silver Plume6a centers mainly in the engineering feat of scaling the steep mountain side and in the fine views he obtains during the ascent. After zigzagging back and forth up the steep side of the valley the train passes around a point and runs up another valley to its head and then, after making several switchbacks, finds its way to the summit of Mount McClellan. The view from this point is shown in Plate IX. Mount McClellan is not on the Continental Divide but on a high spur that branches off from it toward the east. The water that falls on both sides of this peak finds its way into Clear Creek and eventually reaches the Gulf of Mexico, but that which falls on different sides of Grays and Torrys peaks,7 which are on the Continental Divide, runs into streams that flow in diverse directions, part of it reaching the Gulf of Mexico and part of it the Pacific Ocean. These peaks are all more than 14,000 feet in altitude and are prominent features that may be seen toward the west, but they do not appear to stand so high above their surroundings as Pikes Peak and some other well-known mountain summits.
6aSince the description of the trip to Mount McClellan was written the line has been abandoned, and the traveler will have no opportunity to reach the summit of the mountain except by private conveyance.
7The altitude of Grays Peak is 14,341 feet; Evans Peak, 14,260 feet; Torrys Peak, 14,336 feet; and Mount McClellan, 14,007 feet.
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| PLATE IX. MOUNT McCLELLAN. Summit of Mount McClellan (on the right), 14,007 feet above sea level, and Grays and Torrys peaks on the Continental Divide (on the left). Note the great amphitheather or cirque about 2,560 feet deep in front of these peaks. The cirque was largely excavated by a glacier that flowed to the north (right) by Silver Plume and Georgetown. Photograph furnished by the Argentine & Grays Peak Railroad. |
The slope on the east side of Mount McClellan is smooth and gentle, but that on the west side is precipitous, because the snow and ice that long ago lay on the west side, under the shadow of the towering summits of Grays and Torrys peaks, were more protected from the sun and wind than those on the east side, and consequently, during the great ice age, an enormous glacier lay in the angle between Mount McClellan and Grays Peak and cut out a great amphitheater in the rocks, which, because of its circular form, is called by geologists a cirque. If the traveler standing on the ragged crest of this old cirque and looking down 2,500 feet into it has a vivid imagination, he may still see the great glacier that once filled it and flowed down the valley nearly to Idaho Springs.
The route followed by the traveler throughout this trip is practically parallel with a high-tension electric transmission line of the Colorado Power Co. The power is developed at a large hydroelectric plant on Colorado River above Glenwood Springs and is carried to most of the mining camps in the mountains, crossing the Continental Divide three times and finally descending on the east to Georgetown, Idaho Springs, and Denver. The line may be distinguished by the high steel towers and the strip of cleared land along its right of way.
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Last Updated: 16-Feb-2007