Mineral depsoits on furnace blower

[mikek]

While changing my furnace filter, I was alarmed to see a heavy buildup of a white mineral deposit on the furnace blower. It looks like the mineral deposits caused by my hard water. I've had a furnace humidifier unit for nearly 8 years. I had an AC unit installed in 2009. I'd like to believe that if the deposits are from the humidifier, I would have noticed them before now. Could the deposits be from the AC unit? What causes it, and what should I do about it?

I posted a picture - *.*/file/v7d8fd

Thanks,
Mike K