Cape May diamonds
Cape May diamonds are quartz pebbles found on the beaches of Cape May Point, New Jersey. The pebbles are sometimes collected, cut and polished to resemble diamonds, then sold locally as souvenirs. Cape May diamonds are usually collected by beach combing and are most abundant at Higbee and Sunset beaches in Cape May. Cape May diamonds range in size from the finest sand to a "Cape May diamond" found in New Castle, Delaware in 1866. In the 1960s a small intact quartz crystal was found at Sunset Beach which showed almost no signs of rounding by erosion. This dispelled some early myths of their source which included a large boulder of quartz offshore.
Origin
Cape May diamonds are actually pieces of quartz washed down, and worn smooth in the process, from the upper Delaware River. Apocryphally, the trip takes thousands of years. However, geologists suggest the pebbles are local in origin, washing out of nearby Pleistocene gravel deposits.Cape May diamonds are sometimes incorrectly described as river-smoothed glass discarded by New Jersey's once-thriving glass manufacturing industry.