Pt.5) Durability and Condition of the Stone: Building Stone of the Lincoln Memorial, by Elaine S. McGee

An investigation of differences in the durability of the Colorado Yule marble, a widely used building stone.

By Elaine S. McGee.

U.S. GEOLOGICAL SURVEY BULLETIN 2162

Building Stone of the Lincoln Memorial

Abridged and Presented for your Interest and Entertainment by Martin Cooney

PART 5) DURABILITY AND CONDITION OF THE STONE

U.S. Department of the Interior / U.S. Geological Survey

Colorado Yule Marble — Building Stone of the Lincoln Memorial. Prepared in cooperation with the National Park Service Colorado Yule Marble — Building Stone of the Lincoln Memorial By Elaine S. McGee. U.S. DEPARTMENT OF THE INTERIOR: BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY: CHARLES G. GROAT, Director UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1999. Published in the Eastern Region, Reston, Va. For sale by U.S. Geological Survey Information Services Box 25286, Federal Center Denver, CO 80225 Library of Congress Cataloging in Publication Data. Manuscript approved for publication August 13, 1998.

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DURABILITY OF THE MARBLE IN THE LINCOLN MEMORIAL

By Elaine S. McGee

Yule marble was a new and relatively unknown marble

One of the concerns that were raised about using the Colorado Yule marble for the Lincoln Memorial was that no one knew whether it would prove to be a durable stone.  In an effort to address that issue, prior to the selection of the marble for the Lincoln Memorial, laboratory tests for durability were performed by the Bureau of Standards on the five marbles submitted for consideration by the Lincoln Memorial Commission.

The Lincoln Memorial Commission

The Bureau of Standards concluded that resistance of the marbles to weathering would be best determined by a comparison of structures made of the marbles. The other marbles that were proposed for the memorial had been used in a number of buildings, and so it was possible to anticipate how those marbles might appear years after the memorial was built.  However, when the Lincoln Memorial was being built, the Yule marble was a new and relatively unknown marble; few buildings had used the Yule marble.

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CONDITION OF THE MARBLE

Deterioration features typical for marble used in buildings

The marble in the Lincoln Memorial has deterioration features that are typical for marble used in buildings. Although some cracks exist in the marble of the Lincoln Memorial, few of the cracks resemble the “rifts” that were of such concern in the Cheesman Memorial (Denver, Colorado).

On the upper areas of the Lincoln Memorial on the penthouse walls and along the entablature, in particular on the cheneau and antefixae, exposed surfaces of the marble have a sugary texture, and some stones show differential wear on the exposed surfaces, where the marble surface has weathered unevenly. Inclusions of quartz or feldspar, particularly in some of the stones around the roof entablature, stand higher than the surface of the calcite grains because they are more resistant to weathering.

Most of the surfaces are washed by rain

The column shafts also show a differential weathering of inclusions or a localized pronounced variation in stone quality, where there are chalky white areas in the marble. There are very few black surficial alteration crusts at the Lincoln Memorial. This lack of crusts may be because the ornamentation on the memorial is simple with classical lines, so that most surfaces of the marble are washed by rain, and there are few areas where the carving provides recessed and sheltered surfaces in which surficial gypsum is likely to accumulate.

Gypsum accumulation might also be slowed in many areas of the building because the National Park Service regularly washes accessible surfaces of the building. The main area where black crusts are visible at the memorial is on the guttae, on the cornice underside of the roof entablature.

Natural antiquing fairly typical of marbles elsewhere

Another characteristic surficial weathering feature on some stones in the Lincoln Memorial is a slight yellowishorange surficial discoloration that is most visible on some of the antefixae and in the penthouse.  Some of this discoloration may be a natural “antiquing” that is fairly typical of marbles, because as the calcite weathers, dirt adheres to the roughened surface.  In areas where the yellowish-orange discoloration is concentrated, bacteria may be growing on or between the calcite grains below the structure’s surface.  Alternatively, some of the orange surficial discoloration may have developed during shipment to the memorial site.

One striking feature of the condition of the marble in the Lincoln Memorial is that while some blocks of stone appear to show little or no signs of deterioration at all, adjacent blocks show mild to severe deterioration.  Stones that have withstood weathering are clear white and hard and retain crisp, well-defined edges on corners and carved features.

Contrast in overall stone condition

The presence of inclusions in a block of marble is not correlated with the degree of deterioration of the stone. This contrast in overall stone condition occurs in several places at the memorial but is most noticeable along the roof entablature and on the penthouse walls.

A puzzling aspect of this contrast in stone integrity is that stones which have had identical exposure to weathering agents show such a significant difference in durability. Because the deteriorated stones occur on all sides of the building, it appears that exposure to microclimatic effects around the building is not an adequate explanation for the variability in the stone surfaces.

Tooling of the stone surfaces may cause minor variations

Similarly, because of the distribution of the affected stones and because there are no visible unique characteristics of the stones other than the sugared surface, it seems unlikely that salts moving in the stone or accumulating on the stone surface are the cause of the variations.

Although tooling of stone surfaces may cause minor variations in the stone that weaken the stone or make the surface more susceptible to weathering, this seems an unlikely explanation for the stones at the Lincoln Memorial.

All of the stones were finished at the fabricating mill in Marble, Colorado

All of the stones at the Lincoln Memorial were finished at the Yule fabricating facility in Marble prior to shipping to the memorial. If finishing of the stone caused the surficial variations, then the variations would not be distributed randomly around the memorial.

Instead, the badly sugared surfaces would be restricted to stones with specific types of carved features, or to stones processed during a limited period of time when the usual stone handling procedures were not followed.

Difference in integrity arises from some characteristic feature of the stone

Although the variable stones are most noticeable on the penthouse walls and on the roof entablature, variations in the surface roughness are found all over the building on many types of architectural features, and it seems unlikely that a change in stone procedures at the fabricating plant could have affected the stones in such a random fashion.

It seems more likely that the difference in integrity arises from some characteristic feature of the stone, which is probably an inherent feature of the marble.

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An investigation of differences in the durability of the Colorado Yule marble, a widely used building stone.

By Elaine S. McGee.

U.S. GEOLOGICAL SURVEY BULLETIN 2162

Building Stone of the Lincoln Memorial

Abridged and Presented for your Interest and Information by Martin Cooney

PART 5) DURABILITY AND CONDITION OF THE STONE

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Next

PART 6) VARIATIONS IN THE YULE MARBLE …. Click Here

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The Story of Colorado Yule Marble

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thanks for visiting martincooney.com

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