Take the chert nodules. (some call it flint) Nodules around here are about softball size on average. Almost round to egg shaped concretionss of limestone.
It is hypothesized that they would bury several about 8-12 inches under a fire pit, ring or hearth-whatever. Do as normal and just leave the stones under there for a few days while and everyday fire was used above for general purposes.
After the desired time, they nods were dug up and they were fractured by concussion to reveal the spalls they needed to proceed with a workable flake and so on.
Similar in theory like our local historical iron-ore furnaces from the 1850s here. Hematite enriched limestone was heated until it melted like glass, the glassy slag went to the spoils pile, the pig iron flowed into the ingots.
Around here, many gravel roads have blue glassy slag from the 1800s industrial waste spoils.
Here is a large hafted chopper with what help. The top edge reveals a glassy sheen, this is dry right off the bookshelf. This is the thing I could grab with digging through boxes and buckets.
Hope this helps
Gawd I remember when he found that I about chyt my pants.
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