@karatekirk,
This looks like the remnants of an iron "Bloomery". This was an old way of making iron from low grade iron oxides and oxyhydroxide minerals,(often called "Bog ore").
It was a way that earliest iron making was done in the bronze age (Many cultures did use iron during what we call the Bronze age because it was an accidental find in the Carpathians and in the Levant.
The rocks were just piled within a lined pit and a fire was kept going. The ores, (Mostly iron and Magnesium Calcium silicate rocks), would separate into a spongy mass called "iron bloom", the components were iron rich and iron poor denser silicates called forsterite and fayalite.
Stuff was fashioned out of bloom iron but most of it was brittle until the next step "smelting" was discovered much later. Chinese iron ware is very old but, because its mostly bloom iron, is almost all busted up artifact material.Metallurgy and its archeology is, in many folks opinion, mostly developed on bullshit premises, as if iron "followed some progression" of metallurgy)
WHat prt of the world do you live in? Bloomeries in the US were early colonial, used mostly to slightly "enrich" iron from the bog ore . The spongy material was then refined by making pig iron. In Europe and the LEvant, however, you may have an early archeological indicator of a settlement.
Many times these old Bloomwries were kept in use and then just abandoned and covered up with dirt.
When these wre found (mostly by using magnetometers or even the cheapy metal detectors), they were excavated just like the thing you have on your photo. Its either that or a metamorphic contact zone where hydrocarbon rock (like oil shales) could have caught fire and burnt right up to the contact with a non-hydrocarbon rich rock.
A third possibility is this is some piece of artifct froma coal bed fire where the coaly rock (called "boney") has burnt all the contained pyrite and converted it to something like limonite or Goethite and thi too, is nxt to non coal contct.
Actually it could be a lot of things but I thing the iron bloom is my best guess without handling it.