What is blue sediment.. several cups of it when I flushed my new (1 month old) GE electric 40 gal water heater. Reason for draining & flushing the heater is I'm having problems with stubborn air in hot water lines only (but that's another issue)

Checked the cold supply to WH for residue thinking it may have something to do with the copper piping to heater. To do this I connected a hose directly to supply line & bypassed WH & ran about 20 gal into bath tub…no sediment. This fine blue sediment is not found in any other plumbing fixtures in home.

Checked with GE customer support…no help there.

Thanks in anticipation of your response
VGdaKine