Thread: is this asbestos?

While reappointing a stone foundation in the basement of my home build 1930 I was breaking up the crumbling mortar. When I got to the wall entry of the flue of the oil burning furnance the material around the flue which I though was mortar was a soft material that crumbled easily. The surface was yellowed but deeper it was white. This was between the flue pipe and the stone and brick of the foundation. Some this stuff was plastered over the wall around the opening and flaked off but was not heavy like mortar. Could this be asbestos?
Joe

Photo would help. Short answer - it could be, or it may not be. Have it tested by a lab to be sure.

It probably is Ab. Treat it like it is. Age and location very reasonable assumption.

Only way to know for sure? have it tested.