shower drain buildup -- what and how ?

[gallilaw]

Our house is about 50 years old. The shower drain has a rock-hard buildup as shown in the photo. Based on web reading, it might be calcium, but I don't know.

I considered chipping it away, but thought it best to get some advice first.

What might it be, and what's the best way of removing it without damaging the pipe and connectors, and without adding to a worse clog down below?

Thanks.

[johnjh2o]

Go ahead and chip it out a little at a time and use a shop vac to suck it out of the trap.

John