Many times concretions contain fossils, like this crab found in Holgate, NJ

Written and photographed by Sara Caruso

As avid beachcombers, we would like to think we have seen everything and can identify it all. But some finds baffle even the best of us and so we turn to the internet for assistance. Among the plethora of misinformation out there, we hope to find the right answer. But sometimes even the most hardened researcher comes up empty handed. And nothing seems to confound the coastal collector more than concretions. These strange looking ancient stones may indeed hide a treasure, but they are not handcrafted stone age artifacts or rare delicate fulgurites, glass created by lightning striking the ground. Instead, concretions are a fantastic glimpse into the past.

Many concretions contain fossils and other pieces of the past. These ancient time capsules formed several million years ago in sedimentary rock when minerals from ground water settled around a nucleus, such as a stone, shell, or fossil. The precipitating minerals act like cement encasing the debris with layers of rock.

The term concretion comes from the Middle Eastern word concret, derived from the Latin concrescere, meaning to grow together or harden. Concretions are important to the ecosystem as the soft stone can provide a holdfast for seaweed or corals, and homes to burrowing bivalves in the Pholadidae family such as the angel wing clam (Cyrtopleura costata).

Concretions vary in size and shape. They can be small or gigantic, random shaped or well-defined form. Many are rounded, even spherical or egg shaped. Some are weirdly symmetrical, almost statuesque, which in the past gave them the nickname “fairy stones” as people believed they were made by fairies. Here, on Long Beach Island, New Jersey we find long stretched-out twisted concretions. Understandably, many people are fooled by their wide variety of unusual shapes. Few people are familiar with concretions. Which leads to confusion and misidentification. Thus, it can be difficult to find help with proper identification.

Many believe the concretion they found is a rare stone age artifact. Instead, what they have found is a geofact, a stone worn and carved by nature that looks like an ancient artifact made by human hands.

Concretions can loo like artifacts, however the stones are too soft to have been used as a tool.

Because they are unaware, others are quick to identify concretions as fulgurites. True fulgurite, which forms when lightning strikes sand fusing it into glass, is fragile and rather rare. Because most beach sand is very fine, the delicate glass structure of a true fulgurite would quickly be crushed by the rolling waves. This misidentification happens so frequently that I have termed concretions, especially those in shapes resembling a lightning bolt as fulguwrongs.

Identifying concretions can be very tricky. Looks can be very deceiving, and many times lead to misidentification. Asking for help on social media is a good way to learn. But it is important to confirm the crowd-sourced identification with further research.

The best time to find beach concretions is after a storm or during a blowout tide. On LBI, they can be found all along the shore, especially at either point in Holgate or Barnegat Light. The shapes of concretions can be deceiving and confusing, but they are worth investigating; these primordial rocks hold bits and pieces of history from our ancient world.

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