[Illustration: The Jefferson Memorial is made of marble and was
dedicated in 1943.]
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.
[Illustration: Several of the column shafts at the Jefferson
Memorial have grooves that follow the inclusion traces in the
marble, where the mineral inclusions have weathered out and been
lost.]
[Illustration: A close look at some of the weathered grooves in the
columns shows that small bits of mica and pyrite remain.]
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.
[Illustration: Part of one of the column capitals at the Jefferson
Memorial broke off and fell onto the portico in 1990.]
The next stop is the Lincoln Memorial, 1.8 kilometers (a little more
than a mile) northeast of the Jefferson Memorial.