UPDATE. Spoke with my plumber. He's not a dishwasher expert, but he
suspects what chipped off the heating element was NOT part OF the
heating element but merely detergent build-up from years of hard-water
use. Now that chalky, caked-on build-up is being consistently
weakened by the vinegar I've been using for about a year. He says the
vinegar won't hurt the machine, it will only continue to clean it, and
I should just forge ahead and enjoy watching my heating element get
cleaner and cleaner.

What threw me is that, with all the build up, my heating element looks
white, and so do images I've seen on-line of dish washer heating
elements. So I looked at one in the hardware store today (for a water
heater). It was copper-colored (no doubt because it's made of
copper).

What chipped off last week was about 1/16th of an inch thick, chalky
white on the outside and dark-colored on the inside...black or dark
green, maybe, like stuff is that comes in contact with copper?
Thoughts?

RW