What is this?

Found this on the sub-flooring of a 120 year old perperty. No water or moisture present. No damage to wood.

Anybody ever see this?

What was its consistency?

Hard like stone?
Crumbled when touched or disturbed?

Looks like a mud ball or remnant of a concrete form board to me.

What did it smell like? Did you taste it?

Looks like spray in insulation that got wet.
Notice the staining from water or liquid that has migrated into the wood.
Was the home insulated lately?
Might have been from start-up of the blower and aimed upwards to through out any materials that were embedded in the hose.
I would have aimed at the floor or if outside ‘‘best place to be’’ aimed in a neutral direction.
Home owner might have insulated the walls or attic him or her self.
Just questioning.

NO I did not taste it. No smell. Hard, I sliced a section off. No insulation installed. Apears to be growth to me. No damged to wood. Found in only this one area in the center of the basement with no moisture available.

Mr.Mull .
I am leaning towards.
In appearance it looks like-
Types of Blown-Fill Insulation
The most common types of materials used for blown-in insulation include cellulose, fiberglass, and mineral (rock or slag) wool. Cellulose is primarily made from recycled newsprint. Most fiberglass contains 20%–30% recycled glass and is a manufactured product for this process. Mineral wool is usually produced from 75% post-industrial recycled content. See the table below to learn how they compare.
I have worked around insulators and examined this product.
I try to make mental notes of every and all materials and processes all my life.
I am going to leave you with that,for to me if it was a contaminant I would lean towaeds
Did the home own at any time remove a furnace .
Looks like ‘’ asbestos fibers’’ for I have also been around installers of blown in insulation of asbestos for it was widely used for fire proofing up until 1972 , if my memory serves me right but do not take this as fact please.
It is only observation from photo’s that you have provided.

tree sap omitted from the boards?

It almost looks like a wasps nest and Mr.Mull I see instances of small amounts of the very same material around the room and on the walls.
Again please describe the consistency of the material.
Hard like what soap rock , soft like wool feathers bread,fibered like fiberglass lint from a drier, we would need more to go one to predict what it could possibly be.

This was a hard material. No oder. I cut a piece off with my knife and it broke apart and crumbled. No insulation going on anywhere. Apears to be a growth. I have done well over a thousand inspections and have neer come across this.