OK, Maybe two dragonflies flying united, LOL.
I made an interesting discovery a few years back. Many landscapers sell creek gravel as a smooth alternative to limestone. I live along a small creek that runs into a major river about 4 miles away.
There is a calm backwater just shy of the river where they have mined "creek gravel" for years. The stuff is loaded with fossils of ancient worms plant stems and all kinds of Permian stuff.
Best wishes!