Yule Marble is a marble of metamorphosed Leadville Limestone found only in the Yule Creek Valley, in the West Elk Mountains of Colorado, southeast of the town of Marble, Colorado.Marble Quadrangle, Colorado; USGS 7.5-minute series topographic quadrangle, Dated 1960, revised 1987 Discovered in 1873, it is quarried underground at an elevation of above sea level—in contrast to most marble, which is quarried from an open pit and at much lower elevations.
The localized geology created a marble that is 99.5% pure calcite, with a grain structure that gives a smooth texture, a homogeneous look, and a luminous surface. It is these qualities for which it was selected to clad the exterior of the Lincoln Memorial and a variety of other buildings throughout the United States, in spite of being more expensive than other marbles. The size of the deposits enables large blocks to be quarried, which is why the marble for the Tomb of the Unknown Soldier at Arlington National Cemetery, with its die block, was quarried from Yule Marble.
Yule's quality comes at a high price due to the cost of quarrying in a high-altitude mountain environment. This challenge has caused the industry and the town of Marble to undergo many boom-and-bust periods since quarrying started in the mid-1880s, making the town emblematic of the economic fluctuations that beset a single-industry economy. Technology advancements in quarrying machinery and transportation have reduced, but not solved, the cost problem that afflicts the operation.
Geology
Development
The forces that created Yule Marble make it distinct from all other American marbles. It was formed by contact metamorphism, unlike Vermont marble and Georgia marble, which are the result of regional metamorphism, a process more associated with the orogeny and erosion of mountain ranges on a regional scale. Geologists still debate over Tennessee marble which did not undergo the same type of metamorphism, leaving it in a very unique property somewhere between metamorphic marble and sedimentary limestone.
In evaluating the marble cross-section, the United States Geological Survey found the marble is bounded above and below by unconformities. This lack of conformable contact resulted in the early dating of the limestone as Silurian rather than the currently accepted Mississippian. The lack of conformable boundaries in exposures along the Treasure Mountain dome explains the variation in reported thicknesses in the quarry area west of Yule Creek of about southeast of the quarry. The overlying Pennsylvanian Molas Formation was an argillite unit which was converted to hornfels and quartzite. Stratigraphically below the Leadville, the chert bearing Devonian Dyer Dolomite Member of the Chaffee Formation was altered by the metamorphism to impure silica-rich marble and occasional serpentine-bearing marble.
The Yule Marble is a metamorphic facies of the regionally distributed Leadville LimestoneUSGS.gov :Leadville Limestone, Williams Canyon Limestone, Manitou Limestone, and Sawatch Quartzite, limestone names of Mississippian age deposited 350 million to 324 million years ago. The Leadville within the Yule area was transformed by contact metamorphism that occurred during the latest Eocene and Oligocene epochs (34 to 28 million years ago) associated with the intrusion and uplift of the nearby granitic Treasure Mountain Dome. The uplift of the Treasure Mountain Dome tilted the limestone away from the intrusion resulting in the marble bed dipping at an angle into the mountain. The marble unit along with older and younger adjacent units in the Yule Valley have a north-northwest strike paralleling the valley and variable dips of 35 to 50 degrees to the west-southwest.Gaskill, D.L. and Godwin, L.H., 1966, Geologic map of the Marble quadrangle, Gunnison and Pitkin Counties, Colorado: U.S. Geological Survey, Geologic Quadrangle Map GQ-512, scale 1:24000 This local contact with the heat and pressure from the intrusion of hot granitic magma recrystallized the Leadville Limestone into a distinctive white marble. Although the Leadville Limestone covered hundreds of square miles and was the ore host at the Leadville mining district, the Yule Creek Valley is the only known location of marble in the region. When the magma cooled, it crystallized into granite.
This local geological activity resulted in a type of marble that is 99.5% pure calcite, with trace amounts of non-calcite inclusions (mainly quartz), and has a density of . The non-calcite inclusions were caused through penetrations along the seams created by the dome uplift rather than through metamorphic contact with the uplifted dome. Though marble is on both sides of the creek, the only visible marble is the seam of the present-day quarry on the west side of Yule Creek.Table to right: "Chemical analysis reported on Yule Marble; Colorado Yule Marble: Building Stone of the Lincoln Memorial, US Geological Survey, 1999, Bulletin 2162, p. 4
Timeline Development of Yule Marble is put into context with Colorado geology by showing the passage of time from earliest rock units to the present with "Ga" = billions of years ago and "Ma" = millions of years ago.
Start End Geologic activity 1.78Ga 1.65Ga Colorado forms (age of oldest exposed rocks found to date). 350Ma 324Ma Leadville Limestone formed in a shallow, warm sea that covered Central Colorado through the accumulation of calcite from the remains of marine life. Today that limestone, which became Yule Marble, is above sea level. 300Ma 248Ma Ancestral Rockies start and eroded away. The town of Marble was located at the edge of the Ancestral Rockies. Limestone was stripped away by erosion leaving the rest buried until 72 million years ago. 248Ma 70Ma Area was a flat coastal plain over which dinosaurs roamed and during the later part was covered by another shallow sea. 72Ma 40Ma 1st of 3 uplifts (Laramide orogeny) of present-day Rockies but partially erodes. 34Ma 28Ma 2nd of 3 uplifts of the present-day Rockies. Volcanic activity with magma intrusions pushing up from below crystallized the limestone into marble. When the magma cooled it crystallized turning into granite. The upward push of the magma against the limestone resulted in the marble being tilted upward and way from the intrusion, creating the 7-mile diameter Treasure Mountain Dome. The town of Marble lies at the edge of the dome. 25Ma 5Ma Colorado Mineral Belt forms 10Ma Present 3rd of 3 uplifts of the Rockies – Colorado
Characteristics
It is the grain of Yule Marble that gives an appearance of smooth texture, a homogeneous look, and a luminous surface that polishes well. These qualities are why it has been chosen for a number of major national and state landmarks, most notably the Lincoln Memorial. Because of its aesthetic value, architect Henry Bacon successfully urged that it be used to clad the whole exterior of the Memorial, even though it was the most expensive material.As of 1992 there were four grades of marble sold that had variances of grain size and density.
The overall configuration of the grain is small, irregularly shaped, generally equidimensional to slightly elongated with irregular edges and does not vary significantly among the different grades (in 1992). The edges of the calcite grains are deeply crenulated (irregularly and minutely notched and scalloped). Grain sizes range primarily from 0.1 mm (0.00393 in) to 0.6 mm (0.0236 in), as determined by scanning electron microscope images. There are 2,000–3,000 grains to the square centimeter (0.1550 square inches). Where the marble is in direct contact with the intrusive granite, the most consistent change in the marble is that it becomes extremely coarse-grained, with the grain size in the contact zone being 10 mm to 20 mm (0.3937–0.7874 inches). The grains in turn are tightly bonded in the shape of a jigsaw puzzle, forming crystals which are aligned so that the long axes of the grains are essentially perpendicular to the principal veining in the deposit.
When marble does break down, the cause is weak boundaries between the grains that permit water or solutions to penetrate into the marble. As water enters, the calcite grains dissolve slightly, and the opening between the grains widens. With time, as the grain openings widen, the edges become smooth, and the grains become rounded. As the surface grains become round, they loosen and fall off the surface of the stone. Because Yule Marble is finely grained with tight bonding, water is not likely to react as quickly as with a coarse-grained, loose-textured marble. Also the crenulated boundaries of Yule Marble crystals may account for the weathering resistance, because the spaces between grains must be widened enough to free adjoining crystals.
Included in the grains are intrusions (non-calcite material) which does not vary significantly among the four grades; tests in the late 1990s confirm the 1910 amount of 0.5%. Constant inclusions in all Yules are magnesium oxide (MgO), manganese oxide (MnO), iron oxide (FeO), and strontium oxide (SrO) while other inclusions vary by quarry location. Inclusions are in four groups: quartz (the most abundant and gray in color); muscovite (mica, occurs as thin gold lines and streaks, and also occurs with quartz in clouds of gray mixed with brown); feldspar (with larger grain size 0.591 inches (15 mm) to 1.379 inches (35 mm) and gray in color but less translucent than quartz inclusions); and pyrite. Other minor inclusions are sphene, apatite, rutile, zircon, and sphalerite. An example of inclusion affect is gold veining, the result of iron or manganese, that is still quarried today.
When the physical characteristics of Yule Marble are compared to the other US marble, the results are about the same for general characteristics of weight, hardness, specific gravity, porosity, absorption, and coefficient of thermal expansion. In strength characteristics, the properties of Yule Marble are lower than most of the other marbles for compressive strength and transverse strength, but they are not unreasonably low. For ordinary uses, stone having a compressive strength of 5,000 lb per square inch is satisfactory. Test results from 1913 to 1937 ranged from 6,694 to 10,195 pounds per square inch (471 to 717 kg per square cm); in 1996, results were 14,874 (1,046 kg per square cm).
Quarry
The same geology that created the marble also created a host of problems in quarrying the stone. Quarrying in this high altitude environment with steep slopes, deep snow, and snow-mud slides is so expensive that advances in technology have not been able to overcome the challenges. These factors limit periods of operation and the amount of marble that can be brought down from the quarry. In the early years a lack of transportation to move enough of the stone out of Marble added to the difficulties. The transportation problem was largely mitigated by the advent of a railroad (1906 through 1941) and by road and truck since 1990. The cutting rates of today's equipment are much faster than the 1911 technology.
Located along and above the east and west side of Yule Creek, from an elevation of to were five quarries, of which only one on the west side is in operation today. Those on the west were the most productive being the John Osgood quarry (pit-type started in the early 1890s) and the present-day quarry started in 1905 by the Colorado-Yule Marble Company inside the mountain. The east side quarry, started in 1904 by the Strauss brothers, was quarried inside Whitehouse Mountain. Most marble quarries in the world today are pit-type operations, such as Carrara, Italy. The amount of Yule Marble remaining for quarrying should last for hundreds of years.