its acrylic,, use a medium sand paper to get rid of it,, no vinegar,, then polish the acrylic and it will be good as new.. google/youtube how to get a scratch out of acrylic aquarium.
basically you are going to have to sand the calcium until you hit acrylic, basically scratching the acrylic then buy the stuff to polish it. it works great. i will see if i can find the name