Starting last week, I noticed a fine metallic dust accumulating on the bottom of my Surface Pro 4 with no apparent source. It clumps around the magnetic spots where a keyboard would attach. I usually clean the metal off with a Q-tip, but the metal just redeposits whenever I drag the bottom of the Surface across my bed sheet or a similar surface. Strangely, this doesn't happen if the outer perimeter of my Surface is sealed with tape. I don't know if the metal is leaking internally or if it is shedding off of the casing. In low concentrations, the metal dust shimmers just like the casing, which leads me to assume the latter. I also don't know if this is a potential health issue I should be concerned about. I've attached photos of a few days' worth of accumulation. I bought my Surface used, and I've owned it since February. The only issues I have with it are a dead strip across the screen (same issue as this person) and unpredictable black screens if the system has slept for a few minutes, in which I have to hold down the power button for ten seconds and then press it to turn it back on (Event IDs 41 & 6008).