mudstone with iron?

[TomC]

I am glad I found this forum. I've always been interested about the origins of rocks. Always amazed how something can be turned into stone given time and pressure. Note my most recent find. This odd shaped stone was unlike any others in the stream and was found in New York State, in Hudson Valley, in the Shawangunk Kill. I took it home (really heavy) and pressure washed it. The side that was down is grey and the topside was green. I assumed the green is algae growth but also thought the pressure wash would take it off. The color seems to be embedded. Likley due to the seemingly porous nature of the grey areas.

I am pretty sure the gray part is clay of some sort turned into stone. I was curious about the ironlike outcrops. Could that be parts of trees, limbs or branches that have also turned to stone? Thank you for helping me to identify.

ps How did I do on the photos? 

Edited July 4, 2022 by TomC