The Origins, Composition and Discovery of Colorado Yule Marble

The STORY of COLORADO YULE MARBLE at MARTINCOONEY.COM

The Origins, Composition and Discovery of Colorado Yule Marble

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The Lincoln Memorial – Colorado Yule Marble Masterpiece

Colorado Yule Marble may be found only in the Yule Creek Valley,  three miles southeast of  the secluded Rocky Mountain town of Marble, Colorado, 9,300 feet above sea level. It was discovered in the spring of 1873 by geologist Sylvester Richardson.

George Yule was the prospector who “rediscovered” the marble in 1874.

In the same year, an unknown person selected several samples of marble and took them to Denver, but for whatever reason, failed to generate much in the way of genuine (moneyed) interest.  The marble duly became lost again, only to be rediscovered 10 years later, and once more by accident, or so the story goes.

What cannot be disputed however was the supreme quality of the Sylvester Richardson/George Yule discovery, for unlike Vermont and Georgia marble, Colorado Yule was formed as a result of contact metamorphism. Prior to Yule’s discovery, all commercial American marble deposits were formed via mountain range erosion on a purely regional scale, with the heat generated as oceanic and continental tectonic plates grind over and under one another.   Meaning that the marbling effect was attained by limestone sinking into the bowels of the Earth and being subsequently ‘baked’ via the friction created at relatively sedate temperatures when compared to those that forged marble born of direct contact with magma.

Average magma temperatures range 700C to 1,300C, or 1,300F to 2,400F, with Komatite magmas reaching unfathomable temperatures, perhaps as hot as 1,600C, or 2,912 Fahrenheit. These almost unimaginably dramatic conditions were responsible for Yule marble’s most admired features, the purity of its calcite, and the intrigue surrounding its quality and characteristics.  Both Vermont and Georgia marble are the result of Regional Metamorphism, and what is known as Tennessee marble is not technically a marble, as it did not ‘metamorph’  from limestone at all. Whereas such was the incredible heat and pressure exerted by the molten-hot layer of magma, or more specifically rhyolite,  upon the sliver of an outcrop of Leadville limestone, as illustrated above, that the intrusions of hot granitic magma recrystallized it into the prized and valued ‘pure’ white marble it is today.  How pure I hear you ask? 99.5 percent pure calcite, that’s how pure.

Not only is the purity of Yule quite renowned, but the dramatic nature of its trace amounts of non-calcite intrusions carry with them hints and hues of blue and green, orange, yellows galore that serve as mysterious highlights to Yule’s swirling clouds of bluey gray streaks.  The four main groups of intrusions are: Quartz, in the form of cooled granite – the signature blueish gray color; Mica, often appearing as thin golden streaks; Feldspar, crystallized from magma, and used widely in the glass and ceramics industries; and Pyrite, with its metallic pale brass-yellow hue, often appearing as bone fide chunks of fools gold.  Greens, blues and the odd yellow tints are often glimpsed courtesy of numerous other minor inclusions such as: Shene, Apatite, Rutile, Zircon, something called Sphalerite, Iron, and Manganese, which I am informed plays a crucial role in fashioning Yule marble’s famous, and incredibly rare, ‘gold’ veins.

Treasure Mountain Dome they called it, and what a boon it proved to be.  Slowly but surely the local economy was realigned around a burgeoning marble industry, while the nearby communities of Crystal and Schofield faded into ghost towns.

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The STORY of COLORADO YULE MARBLE at MARTINCOONEY.COM

The Origins, Composition and Discovery of Colorado Yule Marble

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