Fireback material

[Ben]

Hi,

I'm living in a 1920's lowrise block of flats. In unblocking a fireplace I found the fireback was made of some low density stuff - unsure what. Its not heavy enough to be clay I don't think, but feels very light. Its firm, but I can imagine it might have been some kind of aerated foam that has then set into a shape.

Is this likely to be made of anything unpleasant?

Cheers,

Ben

[Phil L]

How thick is it?

Is it yellowish in colour, and gravelly?

[<me9]

Most likely to be vermiculite cement. Not currently thought to be unpleasant.