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Geologic Column
More valuable than gold, or not
Lisa Rossbacher

The world is full of urban legends: computer viruses that don’t really exist, thieves who steal human organs, dish soap as pesticide, weird ingredients in fast-food hamburgers.

Here’s another one: The very top of the Washington Monument is made of aluminum because it was more valuable than gold, silver or platinum, and because of this value, it was chosen to be the cap of the monument to honor America’s first president. True or false?


The Washington Monument is capped with an aluminum pyramid, but for very different reasons than its value. Since the monument was completed in 1884, the story about the aluminum pyramid’s expense as a way to honor the country’s first president has been reinforced in many publications, ranging from Civil Engineering Magazine to the Washington Post.

Aluminum was indeed rare and costly to produce in the 1880s, when the Washington Monument was completed, but it was not selected because of its cost, and it was not even the most valuable metal around. At a cost of about $1 per ounce then, aluminum cost approximately the same as silver.

“Call me Al”

Aluminum was not the original choice for the pyramid to top the monument. The purpose of the cap was to serve as a lightening rod. The selection of aluminum evolved during negotiations between the engineer in charge of the construction, Colonel Thomas Lincoln Casey (U.S. Army Corps of Engineers), and William Frishmuth, who was the only aluminum producer in the United States at the time. The preferred materials for the cap were copper, bronze or brass plated with platinum.

Frishmuth suggested instead that the pyramid should be made of aluminum, which he estimated would cost $75. Casey accepted the proposal, with a warning to keep within the estimated cost.

Frishmuth was successful in casting a cap that he pronounced to be a “perfect pyramide of pure aluminum made of South Carolina Corundum,” which is an aluminum silicate mineral. The pyramid was 9 inches high and weighed 100 ounces; it was the largest piece of cast aluminum that had ever been created at that time. Frishmuth was so pleased with the result that he asked for permission to exhibit the aluminum pyramid for two days before he delivered it to Washington, D.C. It was displayed “like a jewel” in the window of Tiffany’s in New York — undoubtedly adding to the myth of the value of this new metal, aluminum.

Casey’s response, on delivery of the pyramid, was “the point is received and is acceptable in every way.”

Then he got the bill.

As it turned out, the estimated cost was exceeded — by a lot. The original estimate of $75 had turned into an invoice for $256.10. Casey immediately dispatched his assistant to investigate.

The details about the cost overrun are not altogether clear, although part of the reason was that the typical sand mold would not work for the pyramid’s casting, and an iron mold had to be constructed. Another factor may have been that the cost of the aluminum alone, at the prevailing price, was more than the estimate. The payment was ultimately $225 — three times the original estimate.

The capstone and aluminum pyramid were placed on top of the Washington Monument on Dec. 6, 1884, and the formal dedication was held on Feb. 21, 1885, more than 30 years after construction began. The national media covered both events, and the aluminum tip was featured prominently. The American pubic, most of whom had probably never heard of aluminum before, learned in the press that it was a rare and valuable metal.

Measuring value

The Washington Monument urban legend does make a valuable point, however. The cost — and therefore the perceived value — of metals depends on several factors, including the technology available to extract them, the demand for the product and public perception.

At the time that the metal pyramid capping the Washington Monument was created, aluminum was very difficult to extract. Although it is the most abundant metal in Earth’s crust, it occurs in nature only in tightly bonded compounds. A Danish chemist, Hans Christian Oersted, first isolated small amounts of the pure metal in 1825. German and French chemists invented new extraction methods over the next decades, and the price of aluminum dropped from $1,200 per kilogram in 1852 to about $40 per kilogram in 1859.

Thirty years later, in 1889, Charles Martin Hall, a recent chemistry graduate from Oberlin College, patented a new method to produce aluminum. His approach used an electric current passed through a nonmetallic conductor to separate the highly conductive aluminum. Hall founded the Pittsburgh Reduction Company, which became the Aluminum Company of America — Alcoa — and which remains the leading producer of aluminum in the world today.

Overnight, aluminum ceased to be considered a precious metal. By the time Hall died in 1914, aluminum cost 18 cents a pound (about 40 cents per kilogram). At that cost, the total value of the aluminum in the Washington Monument’s cap would have been $1.62 (in 1914 dollars) — rather than the nearly $100 value at the time the pyramid was cast.

For a contemporary comparison, investment analysts in February 2005 expressed concern that aluminum prices were approaching “record highs” of nearly $2,000 per metric ton, almost $2 per kilogram. At this rate, the aluminum in the cap for the Washington Monument would cost about $5.67 in current dollars.

It just goes to show that you don’t need the most expensive material available to make a great memorial in honor of a great person.

Rossbacher, a geologist, is president of the Southern Polytechnic State University in Marietta, Ga.

Much of the information for this column comes from “The Point of a Monument: A History of the Aluminum Cap of the Washington Monument,” by George J. Binczewski, in the November 1995 Journal of Minerals, Metals and Materials Society.

For more about the geology of Washington, D.C., read "Pedaling D.C.'s monuments," available on the Travels in Geology archive.

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