Each piece is cleaned multiple times before polishing and packing it, but sometimes bits of chemical residue may remain and, over time, result in a white "crust" along the lead lines. You can gently scrub this "crust" with the rough side of a sponge to remove it.
To dust your piece, use a dry cotton cloth, paper towel, or mircofiber cloth. Q-tips or cotton swabs are helpful when cleaning along the lead lines.
Avoid using abrasive or chemical cleaners such as Windex.