A favorite find of mine from the north-central shore of Long Island going back 35 years: a red hematite concretion commonly referred to Indian Paint Pots. These were eroding out of a midden pile habitation site and on their way to the bay shores. Dense with a perfect tight seal, thus, prehistoric tupperware. I like how the geode when closed resembles a human heart. The 1775 Spanish one Real I found close to home a few months ago and is added for scale.