The Quarries

On some of the bluffs overlooking Rock Creek and the small streams that feed it, thousands of cobbles peek through the dead leaves on the ground. These stones may not look like much, but they are the remnants of a prehistoric industry where ancient Indians once made hundreds of thousands of stone tools.

Three Rough Stone “Bifaces” Quarried from the Banks of Rock Creek around 2200 BC

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Most of the cobbles are a very tough kind of stone known as quartzite. Quartzite was seldom used in earlier times, but around 4,500 years ago the Native American residents of coastal Virginia and Maryland preferred it for making a kind of wide, heavy spearpoint we call the Savannah River broadspear. Huge numbers of quartzite cobbles were taken from these hillsides and chipped into roughly oval "blanks" or "performs." The roughly shaped stones were carried to campsites nearby, where they were shaped into finished tools. The quarry sites are covered with millions of fragments of waste stone and many thousands of cobbles that were tested and then discarded.

Photograph of William Henry Holmes.

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The quartzite quarries within the Rock Creek valley have an important place in the history of American archeology. They were studied intensively by William Henry Holmes of the Bureau of American Ethnology between 1889 and 1894. The rough, oval preforms from the quarries look something like the ancient Acheulian handaxes of Europe, made between 500,000 and 100,000 years ago. Before Holmes's research, some American archeologists saw similarities between the local preforms and European sites and thought that people must have lived in North America in Acheulian times. Holmes worked out how a cobble was chipped into a finished spearpoint, and showed that what were said to be ancient hand axes were actually only the middle stages of this tool-making process.

Drawing of Holmes's conception of how a cobble was chipped into a finished spearpoint.

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Drawing of the Profile of one of Holmes Excavation Trenches.

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Holmes's excavations at the Rock Creek quarries represented the state of the art in late nineteenth-century archeology, and it would be difficult even today to improve upon his techniques or reporting. His men dug trenches along the hillsides where the cobble beds are exposed, showing that in some places the debris left by ancient quarrying is five feet thick.

Broken Stone Axe found in one of the Rock Creek Quarries.

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Some of the quarries Holmes studied have been destroyed by the expanding city of Washington, but others remain intact in Rock Creek Park. They were explored by archeologists in 2004. Among the recent finds are whole and broken turtleback cores at various stages of completion, as well as half of a large, crude axe, possibly used as a quarrying tool. Some evidence of tool making was also found, including the tip of a nearly finished spearpoint.

Archeologists are not certain when or for how long the quartzite quarries were used. Holmes did not find any finished spearpoints in his excavations (which could be dated by their distinctive style), nor have any been found at the sites since. The best clue is the material of the stones. Quartzite was used for stone tools at many times in the past, but only the Savannah River people used so much of it that they would have needed these enormous quarries. Most likely, then, the quarries were used from about 2200 to 1700 BC. Those dates come from radiocarbon dating of fireplaces found near Savannah River spearpoints on other sites. Radiocarbon dating only became available to archeologists after 1948, and it requires organic samples, preferably charcoal. As archeologists have tried to figure out the date of the quarries, they are teased by this item in Holmes's account of his work:

In one of the side trenches a good deal of charcoal was found, and at the depth of about 6 feet a charred log more than 10 feet long and in places a foot in diameter was encountered.

Not knowing that radiocarbon dating would one day be invented, Holmes saved none of this charcoal, and we are left to wonder if our guess about the date of the quarries is correct.