silvery patches on chimney?

Some bricks on my chimeny are covered with silvery patches. Under each silvery patch is a black layer. Any idea what these are? They seem to be wearing off.
The house is 15 years old but I bought it used, so I don't have complete history of repair.
http://www.smugmug.com/gallery/6456116_BKWfr
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It looks to me like some type of plate or flashing was adhered to that side of the chimney at one time. Looks like it was peeled off though. Did you or the previous owner have the roof done lately? I doubt it is anything to worry about.
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james wrote:

Those are used brick. They could have been part of almost anything before they went into your chimney, but I'd bet they were part of a road. Had I been the mason, I'd have hidden that side. Perhaps the mason thought they were quaint.
--
Steve Bell
New Life Home Improvement
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