The fireplace looks more turn of the century than 1850 to me but no matter. The red and black brick and the (metal?) hearth are certainly not original. I’m restoring an 1850 fireplace now that had been removed a century ago. It was originally built to be wood fired, than later converted to be coal (opening and firebox reduced in size, metal surround added). It was originally built with a brick hearth and a plaster surround around the firebox opening. For you I’d start by removing the tile, metal surround, and metal hearth. Do you find anything original? If not you could replace the hearth with poured concrete, brick, or a slab of granite. The surround could be smooth plaster, tile, or stone.

@J Wilson

Your fireplace looks very similiar to ours which is brick. Yours looks like it was converted to coal at some point based on the grates. Wood burns from the top down, but coal needs air underneath the fire. But I could be wrong.

I think there is brick underneath the ”interesting” steel.

This is our fireplace. Like yours, the chimney was removed.