Cape May Point, New Jersey
Cape May Diamonds
Clear quartz pebbles that turn up on the bayshore beaches at the tip of New Jersey. Cut and polished they look enough like diamonds to be worth selling, which is how they got the name. Everything about what they are is settled. Where they come from is not.
What they actually are
Quartz. Hard, clear, crystalline quartz — about a 7 on the Mohs scale, which is hard enough to take a polish and hold it, and hard enough to survive a great deal of being knocked about by water.
They run from grains of sand up to something you could close your hand around. A specimen weighing 3 pounds 14 ounces was found up the bay at New Castle, Delaware, in 1866.
Raw, they look like dull cloudy pebbles and most people walk past them. Tumbled and faceted they look startlingly like the real thing, which is why the shops at Sunset Beach have been cutting and setting them for generations.
Where to look
Sunset Beach
The famous one. Coarse pebbly sand at the western end of Cape May Point, and a gift shop that will cut what you find.
Higbee Beach
Up the bayshore, quieter, and every bit as productive. Worth knowing, for reasons that turn out to matter below.
Both are on Delaware Bay, not the ocean. Wave-sorted pebble beds are what you are looking for — the coarse stripe of gravel that a receding tide leaves behind. After a blow is better than after a calm week.
The origin story, and the problem with it
The traditional account, which you will hear at the beach and read almost everywhere, goes like this: the quartz weathers out of veins and pockets up around the Delaware Water Gap, falls into the Delaware River, and is carried more than two hundred miles downstream over thousands of years, being rounded and polished the whole way, until it washes up here at the bottom of the bay.
It is a wonderful story. It may not be true.
Geologists have a duller explanation. The long journey down the river is described in the literature as apocryphal, and the pebbles are attributed instead to nearby Pleistocene gravel deposits — ancient gravel beds close by, which the sea is simply washing out. That reading is backed by New Jersey's own geological sources going back a long way.
There is a piece of physical evidence too. A small quartz crystal found at Sunset Beach in the 1960s was essentially unrounded — still sharp. Nothing survives two hundred miles of river with its edges intact.
The honest position: the stones are hydrothermal vein quartz, and they got here from somewhere. The two-hundred-mile version is local tradition rather than established geology, and the local-gravel version is what the geologists actually argue for. Enjoy the tradition; do not repeat it as fact.
And does the shipwreck concentrate them?
You will also be told that the sunken concrete ship off Sunset Beach breaks the tidal current and traps the stones on that stretch of beach, which is why they gather there.
Nobody has demonstrated that. It is a local attribution rather than a geological finding, and there is a simple objection to it: Higbee Beach has no shipwreck and produces just as many stones.
If you take some home
Check the rules for the beach you are on before you fill a bucket — Higbee Beach is a state wildlife management area and is managed differently from a public bathing beach. A pocketful of pebbles is not the same thing as a haul.