What is this mysterious blue powder that keeps collecting on the inside of our window and sill?

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  The window, sill and apron before we made any changes [aside from the painting]. :)
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  Exterior of the house, window in question...
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  This is the side of the window that shows the largest concentration of the "blue stuff" mostly in the corner [not seen in this shot], but is even visible to th...
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  Another view of the left corner.
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  View on the left side of the window of the piece that is broken [prevents the window from staying up without being propped - newer version of a sa...
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  Another view of this same piece that is broken.
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  We have noticed this blue fluff on the latch and above.
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  You can see whatever this stuff is, how it collects in drifts on the inside. We have not seen this stuff on the outside of the windows.
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