Sea Coal Mystery
Black sand and rocks on beaches are often misidentified — its source has an intriguing history
Last winter, on an unseasonably warm February afternoon, my sister and I were collecting rocks just east of Moonstone Beach — a protected preserve near my home. "I found one," my sister yelled out, lifting up an iridescent black rock that glistened in the sunlight. We examined it together and determined it was probably the namesake stone, a moonstone, due to the dark purple iridescence. As we collected a few more of the rocks along the shore, we noticed how light they were and how numerous. We began to speculate they might actually be a type of pumice. After some Googling, I started to suspect we found something else — an out-of-place rock known more for its industrial use: coal.
"Sea coal," as it's called when it's strewn across a beach, has been found along the Northern Atlantic for centuries. Records of settlers searching for it along the coast of Long Island go back to the 17th century. It's thought to accrue through natural sources or spillage from coal powered steam ships. Finding the source of the sea coal we found led me to dig into recent and some not so recent history.
Although it’s often associated with industrial sources, coal forms naturally from the pressure of earth against decaying plants and other bio-matter. Over time the carbon rich mass forms dense rock. This forms different types of coal, including the hard and dense type called “anthracite” is usually what is found on beaches. When anthracite rock breaks off from an outcrop near a river, its buoyancy — due to its high carbon content — carries it down stream and into the ocean.
Coal can also be transported by glacial activity, landing further inland in clay pits and sand deposits. Rainwater can move coal into the ocean — typically lignite or sub-bituminous coal. It can also float away during a high tide or storm, landing strewn on beaches hundreds of miles away. Centuries of tidal forces can pulverize it into dust, creating patches of black sand.
Along the rivers of the Appalachian Mountains, there are numerous natural outcrops of coal. Deposits can dislodge and end up in rivers.
Coal is rich in carbon and is buoyant enough to be transported downstream and into the Atlantic Ocean.
Coal can be carried as far north as New England, landing on beaches and is sometimes mistaken for more exotic types of rocks.
There is another major source of coal on the east coast — shipwrecks. During the second World War, German U-boats would lie in wait off the beaches of the eastern seaboard. They had sunk over a hundred American commercial and military ships throughout the war. Most ships had large amounts of coal on board to power their steam engines. After the doomed ships landed on the seabed, their coal would drift away with the tide, eventually finding a spot on beaches like Moonstone Beach — along with the occasional lobster trap or piece of driftwood.
Moonstone Beach is located a mile or two east of Point Judith, RI where one of the last naval battles of WWII had taken place. On May 5th, 1945, the German U-Boat 853 sunk a coal transport ship, the Black Point, in the waters off of Pt. Judith, killing 12 of its 45 crewmen. After a days-long hunt, an American Navy destroyer and a number of other ships were able to track and sink the German U-boat. Its hull became a watery tomb for its crew; its coal reserves likely spilling out onto the ocean floor.
A enhanced picture of the ill-fated Black Point
A enhanced picture of the ill-fated Black Point
After my sister returned home, she sent me a link to a rock tumbler she found on Amazon and thought I should buy. Lignite can be shined up as sold as a "jet," a valuable black gemstone made from coal. I sent her some of the history I had uncovered in return. Coal floating down the Delaware River for millions of years and finding its way to the beach; glaciers dragging rock across the ancient landscape and into her collection; or a fateful sinking at the end of a world war. What remains of history are often things we find in the dirt and sand. Sometimes strewn along an otherwise pristine Atlantic beach.
Sea coal found along the coast of Rhode Island.
Sea coal found along the coast of Rhode Island.
List of Sources
1. Fighting U-Boats in American Waters. Nation
Museum of the United States Airforce.
https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/
Display/Article/195991/fighting-u-boats-in-american-waters/
2. The Story of Atlantic Sea Coal Deposits. Geology of the New York City Region. https://gotbooks.miracosta.edu/gonp/nyc/shoreline/seacoal.htm
3.
https://oceanexplorer.noaa.gov/technology/development-partnerships/
18kraken/u853-blackpoint/u853-blackpoint.html
4. Varoujan Karentz. German U-Boat U-853 Stripped of Some of Its Major Artifacts. http://smallstatebighistory.com/german-u-boat-u-853-stripped-of-some-of-its-major-artifacts/
5. Flint, Martha Bockée. Early Long Island, a colonial study. https://archive.org/details/cu31924025959390/page/22/mode/2up?q=%22sea+coal%22
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