Strange looking boulder in forest

[reedm]

Came across this odd, small boulder (about 3 feet across) while hiking in a forest in Illinois. I could find no other similar rocks anywhere in the area.

The weathering pattern was very interesting. It almost looks like its melting. I don't know much about rocks and I assume it's weathered limestone(?) but would appreciate any thoughts from the forum members.

Thanks for your time. -Reed

Attachments:

[scottr]

glacial?

[foxtail]

metamorphic limestone?

[bennet]

I looks like a giant geode to me?

[phyllis]

Was it "fuzzy" (fibrous)? Looks like nepheline syenite (actinolite asbestos wiggley serpentines) from the picture. Was it a light color grey/off white/pink/even a light bluish? We live here on the northshore of Boston on a nepheline syenite dyke...and if it rains a lot, the rocks grow hair..