On Wed, 23 Jun 2010 07:30:51 +1000, Rod Speed wrote:

They are so highly polished because they need to be very smooth since
the heads fly so close to the surface so the magnetic domains are as
small as possible so the bit density is as high as possible.

I thought they were reflective mirrors for the lasers or something.

I didn't realize these were the actual magnetic material. They are soooo
smooth and shiny. I expected concentric circular lines of something or
other like the bottom of a CDROM or DVD once it has been burned.

These platters are so polished that you can't make out a single bit of
"thin oxide" coating. Shinier than any metal or plastic mirror I've ever
seen and more indestructible than glass.

In short, they're the perfect wet-shower traveling mirror if TSA will allow
them through.