Its interesting But I think its a rock that has been dumped as beach ballast nd is not naturl.
Its a form of serpentine called "Pa Jade". There are a number of quarries in SE Pa and Delaware and around havre de Grace Md that mine the rock and the Md Dept of Transportation uses them as rocks for spits, groins, beach ballast and road mixes.
This on isn't "rounded" enough for me to consider it a "Glacial erratic"
There are huge deposits of glacial erratics that occur in the Chesapeake bay and back waters of the Nanticoke. These were rocks that were scoured by the glaciers and, many times, big chunks of ice were calved off the glaciers and picked up "country rocks' As they were carried south by the glacial outwash of the post glacial Susquehanna and Chesapaeake bay. The usual erratics are well rounded, huge chunks and are usually diorites, sandstones, quartzites or rhyolites from along the Susquehannas flood plain.
If you kayak out around some of the islands on the Chesapeake, you can find deposits of these erratics along with caches of the Post Paleo -Transitional encampments and more permanent villages of the Nanticoke People.
You can see the linear piles of these erratics that define the outsides of their plaisades in 20 or 40 feet of water. You can dive to these piles just don't take anything as the clam cops keeps a fairly good eye on archeological sites
FBM was right, these serpentines are 60% or more asbestos of a type called Amosite and it will exfoliate into asbestiform "shards" as it dries. The Pa jade portion is another Mg Silicate that can be polished into tumbed jewelery but its rather soft (hardness <5)
We don't use this kind of rock on Pa hiways because of its nvironmental concerns for asbestos DUST