Part 2

The Jefferson Memorial is a marble building, dedicated in 1943. One of the most striking deterioration features to observe here is the loss of silicate mineral inclusions in the marble columns because of dissolution of the calcite matrix. Close examination of the grooves shows flakes of mica and sometimes grains of pyrite. Blackened crusts are visible on the column capitals that are sheltered from rain and from regular washing of the monument.

The National Park Service began a survey of the condition of this memorial and the Lincoln Memorial in 1992. The results will be used to help make decisions on treatment, cleaning, and preservation. The information gathered from the survey will serve as a known baseline for the condition of the stone, so that future changes in the condition of the buildings can be assessed. In May 1990, a part of one of the column capitals (called a volute) broke off and fell onto the northwest portico. This failure raised concern about all the volutes at the Memorial, so several other cracked volutes were removed, and studies are being conducted to determine why they cracked. Because of where and how the volute broke, it is unlikely that acid rain or air pollution contributed to the failure. The broken pieces will probably be replaced, but only when the reason for their failure is understood, so that an appropriate replacement technique can be chosen.

The next stop is the Lincoln Memorial, 1.8 kilometers (a little more than a mile) northeast of the Jefferson Memorial.

Lincoln Memorial—Site 6

The Lincoln Memorial, dedicated in 1922, is made of marble from Colorado. This building has few alteration crusts, in part because it receives regular cleaning and in part because of the design of the building. Except for the features around the entablature (the edge of the roof), there are few sheltered areas where alteration crusts can accumulate. With the aid of binoculars, you can see some alteration crusts along the underside of the roof overhang; in these places the marble is very badly crumbled under the alteration crusts. Some columns show preferential weathering or loss of inclusions, but some of this damage might be from graffiti removal. The most visible dissolution feature is sugaring, where the stone has lost its polish and the surface now feels rough. Visitors have affected this popular memorial too; several of the columns, especially the limestone columns inside the chamber, show darkening and rounding of edges where visitors have touched them over the years.

One interesting feature at the Lincoln Memorial is differences in stone condition that must come from variations in the stone. At several places around the outside of the memorial, adjacent blocks of marble show very different surface roughness. Since the blocks of stone have the same orientation with respect to wind, rain, and pollution, the difference in condition cannot be due to exposure and must be related to basic characteristics in the stone that was used.

Buildings along 17th Street, NW

Some notable examples of stone deterioration are included in this part of our tour. We will begin this segment at the northeast corner of 17th Street and Constitution Avenue, with the Capitol Gatehouse. We will then cross 17th Street and examine several buildings along 17th Street as we walk north towards Pennsylvania Avenue. The total distance is about three-fourths of a kilometer (half a mile).

Capital Gatehouse—Site 7

This small sandstone building was built around 1828 at the west entrance to the Capitol. In 1880 it was moved (along with a twin and four gateposts) to its present site. This building is made of the same sandstone that was used in the central part of the Capitol and in the White House. Three types of deterioration are readily visible at the gatehouse: spalling, pock marks, and preferential weathering of clay layers in the stone. This stone may be more degraded than stone in the Capitol or the White House, because of variations in stone quality and maintenance to the buildings and because it has never been painted.

To continue, we will cross 17th Street and examine parts of several buildings as we walk north.

Organization of American States Building—Site 8

This marble building was dedicated in 1910. Two sculptures in the front of the building show some alteration crusts in sheltered areas and dissolution in exposed areas. In back of the building the marble balusters on the patio are covered with blackened crusts, especially on the sides facing the garden. In many places the crusts have blistered or spalled off, exposing new surfaces to alteration. In general, the patio sides of the balusters are in much better condition than the sides that face the garden, perhaps because washing of the patio has washed off the gypsum crusts on that side of the balusters.

Continue north through the garden and parking lot and cross C Street to the Daughters of the American Revolution (DAR) Buildings.

DAR—Constitution Hall—Site 9

The main damage on this limestone building, built in the 1930’s, is the blackening of the side balustrade from algae or fungi. The stone is porous and therefore retains moisture, thus encouraging growth of organisms. The limestone in this building is quite uniform and shows little preferential dissolution, except in a few places. On the top of the balustrade along C Street, for example, some of the calcite matrix has dissolved from around the fossil fragments, and some holes are filled with calcite crystals.

Continue east along C Street to Memorial Continental Hall.

DAR—Memorial Continental Hall—Site 10

The porch area on the south side of this marble building built in 1909 is a good place to look at some contrasts in marble deterioration. Parts of the balustrade have been replaced, as shown by differences in color and surface roughness of the stone. The exposed stone surface along the top of the balustrade is rougher than the surfaces in more sheltered areas. The columns on this porch are carved around the base, so you can examine the effects of exposure to rain on the carving details. The more exposed carvings have lost their sharp edges and definition compared to the sheltered carvings. The bases of the columns contain small amounts of pyrite, which is more resistant to weathering than is the calcite in the marble surrounding the pyrite. The sheltered part of the window-sill support on the west side of the porch shows an alteration crust, a dull gray accumulation on the stone surface.

At the corner of 17th and C Streets, turn left and walk north along 17th Street. On our way to the Corcoran Gallery, we will pass the Red Cross building (marble, 1917). Some of the same types of marble deterioration observed at other locations are also present here.

Corcoran Gallery—Site 11

The Corcoran Gallery is marble with a granite base. It was built in 1879 and enlarged in 1927. Ornate carvings around the roof, doors, and windows have blackened crusts of gypsum, as do parts of the marble pedestals supporting the bronze lions at the front door. The marble bases also have inclusions that stand out above the surrounding calcite, which has been dissolved away.

Continuing north along 17th Street towards Pennsylvania Avenue, you will see several modern granite office buildings and the Executive Office building (formerly the State-War and Navy building), which was built from granite and completed in 1888. These granite buildings show little deterioration. Turn right onto Pennsylvania Avenue and proceed to the Renwick Galley on the northeast corner of the intersection of 17th Streets and Pennsylvania Avenue.

Renwick Gallery—Site 12

This building of brick and sandstone, completed in 1859, is interesting from a stone preservation point of view. The decorative sandstone panels were badly deteriorated, so in 1968 the panels were saturated with epoxy to strengthen them. This treatment actually accelerated the deterioration because when water penetrated behind the epoxy-filled area, large portions of the treated panels spalled off. A second renovation attempt was therefore necessary two years after the first, and the present panels are cast sandstone. A post of the original sandstone stands at the southeast corner of the building.

The next part of the tour begins at 15th Street and Pennsylvania Avenue S. To get there, walk east along Pennsylvania Avenue, past Blair House and between Lafayette Park and the White House. Lafayette Park has a number of bronze statues that have been cleaned fairly recently. The White House is built of sandstone that was painted white; the paint was used in part to improve the durability of the stone. After you pass the White House, you will come to the Treasury Building. Turn right onto 15th Street and walk south, towards the Washington Monument and the Mall. The total distance from the Renwick to the corner of 15th and Pennsylvania is about three-fourths of a kilometer (half a mile).

Federal Triangle Buildings—Site 13

On the east side of 15th Street, beginning at E Street, is the Commerce Department building, which was constructed of limestone in the 1930’s. This building is part of the Federal Triangle, a cluster of Federal office buildings in the area bounded by Pennsylvania Avenue, Constitution Avenue, and 15th Street, built primarily during the New Deal administration of President Franklin D. Roosevelt. Some sculptures on the buildings were done by participants in the WPA program. These buildings were cleaned in the 1960’s, probably by sandblasting. Look for fossils in relief and alteration crusts in some sheltered places on the carved work. Some of the blackening on this building is from dirt and organic material trapped or growing in the rough surface of the stone.

Continue south on 15th Street to Constitution Avenue. From the corner of 15th Street and Constitution, follow some of the foot paths half a kilometer (three tenths of a mile) to the Washington Monument.

Washington Monument—Site 14

This monument was begun in 1848, but it was not finished until 1885; the change in color about 150 feet up marks a change in the type of marble used to face the monument. Although it is made of marble, its smooth, straight shape and the massive blocks used in this monument have minimized the effect of acid precipitation. Dissolution does occur in a few areas, but the amount of stone material lost from dissolution is insignificant compared to the mass of the stone.

Our tour ends here, but there are many more stone buildings and monuments in Washington and in other cities that may also show the effects of urban pollution and acid precipitation. However, as seen on this tour, not all of the deterioration of stone buildings is caused by acid rain. To protect our historic stone buildings and monuments, we need to limit air pollution that contributes to acid rain deterioration, and we need to develop effective maintenance and preservation procedures that will not further harm the stone.

Glossary of Geologic and Architectural Terms

Antefix—an ornament along the edge of a roof, often shaped like a shell or shield

Baluster—a post or support for a handrail

Balustrade—a rail and row of supporting posts, especially along a stair or porch

Bronze—a metal alloy of copper and tin; although brown when fresh, it weathers to a more commonly seen green color

Calcite—a mineral composed of calcium carbonate: CaCO₃

Column Capital—The top portion of a column. There are three main types; from least ornate to most ornate, they are Doric, Ionic, and Corinthian

Diabase—a dark-gray to black, fine-textured igneous rock, composed of the minerals feldspar and pyroxene

Feldspar—a common mineral composed of silica (Si), aluminum (Al), and calcium (Ca), potassium (K), or sodium (Na): CaAl₂Si₂O₈, KAlSi₃O₈, NaAlSi₃O₈

Fossil—remains or trace of a plant or animal preserved in a rock from some past, prehistoric time

Granite—a light or speckled, coarse-grained igneous rock composed of quartz, feldspar, and mica

Guttae—small, drop-like rounded ornaments under a roof overhang

Gypsum—a mineral composed of hydrated calcium sulfate: CaSO₄·2H₂O

Igneous—formed from melted or partially molten rock

Inclusion—a mineral phase that is distinct (in composition or appearance) from the main mineral components of a rock

Limestone—a sedimentary rock, chiefly composed of calcium carbonate; formed from the shells of marine animals

Marble—a metamorphic rock, chiefly composed of calcium carbonate

Metamorphic—changed; usually by heat or pressure to a different form but the same composition

Mica—a silicate mineral that forms sheets or layers and contains aluminum, hydroxyl, and alkali ions: K₂Al₄Si₆Al₂O₂₀(OH,F)₄, K₂(Mg,Fe)₆Si₆Al₂O₂₀(OH,F)₄

Mineral—a naturally occurring inorganic substance with an ordered structure; rocks are made of one or more minerals

Portico—a porch, with a roof supported by columns

Pyrite—a mineral (“fool’s gold”) composed of iron sulfide: FeS₂

Pyroxene—a silicate mineral containing two metal oxides: CaMgSi₂O₆, CaFeSi₂O₆, (Mg,Fe)SiO₃

Quartz—a mineral composed of silicon dioxide, or silica: SiO₂

Sandstone—a sedimentary rock composed chiefly of quartz grains

Sedimentary—formed from particles that were transported by water or wind and deposited in layers

Volute—a scroll-like ornament on an Ionic column capital

Further Reading

Acid rain: The facts, 1988: available from Inquiry Centre, Environment Canada, Ottawa, Ontario, Canada K1A 0H3.

Amoroso, G.G., and Fassina, V., 1983, Stone decay and conservation: New York, Elsevier, 453 p.

Hannibal, J.T., and Park, L.E., 1992, A guide to selected sources of information on stone used for buildings, monuments, and works of art: Journal of Geological Education, v. 40, p. 12-24.

Pickering, R.J., 1987, Acid rain: U.S. Geological Survey Open-File Report 87-399.

U.S. Geological Survey, Building stones of our Nation’s Capital: Reston, Va., U.S. Geological Survey general-interest publication.

Winkler, E.M., 1973, Stone: Properties, durability in man’s environment: New York, Springer-Verlag, 230 p.

Photographs by the author · Edited by Kathleen Gohn · Publication design by Elizabeth Junek

★ U.S. Government Printing Office: 1995-394-904

What Type of Rock is It?

Look at the overall appearance of the stone in the building. Observe the color, texture, and structure of the stone.

Does the stone look evenly colored, with an even texture? YES ⇒ Look at the grains up close. Do you see fossil fragments (bits of shells or skeletons)? YES ⇒ LIMESTONE NO ⇒ Are the grains rounded, like sand on the beach? YES ⇒ SANDSTONE NO ⇒ {same as next line} NO ⇒ Do you see streaks or clouds of color in a mostly white stone? YES ⇒ MARBLE NO ⇒ Look at the grains up close. Do you see a mixture of colors (black, white, gray, maybe pink or red)? YES ⇒ GRANITE NO ⇒ MARBLE

Some of these stones may have layers that were the original beds that formed the stones.

The grains in these rocks may look like crystals that fit together like jigsaw puzzle pieces.

As the Nation’s principal conservation agency, the Department of the Interior has responsibility for most of our nationally owned public lands and natural and cultural resources. This includes fostering sound use of our land and water resources; protecting our fish, wildlife, and biological diversity; preserving the environmental and cultural values of our national parks and historical places; and providing for the enjoyment of life through outdoor recreation. The Department assesses our energy and mineral resources and works to ensure that their development is in the best interests of all our people by encouraging stewardship and citizen participation in their care. The Department also has a major responsibility for American Indian reservation communities and for people who live in island territories under U.S. administration.

This publication is one of a series of general interest publications prepared by the U.S. Geological Survey to provide information about the earth sciences, natural resources, and the environment. To obtain a catalog of additional titles in the series “General Interest Publications of the U.S. Geological Survey,” write:

U.S. Geological Survey Information Services P.O. Box 25286 Denver, CO 80225

Transcriber’s Notes

—Retained publication information from the printed edition: this eBook is public-domain in the country of publication.

—In the text versions only, text in italics is delimited by _underscores_.

End of Project Gutenberg's Acid Rain and Our Nation's Capital, by Elaine McGee