material of HDs?

["Adalbert Goertz" <goertza@fatalerr.com>]

re
I think glass and/or aluminum for hard disk platters and
plastic and aluminum for CDs.  The aluminum in the CD
is a very thin disc that does the actual storing.  The
plastic is just to protect it and make it stiff enough for
humans and the CD player or CD drive motor to handle
it.
>>
Adalbert Goertz responds >>>>>>>>>>>>
>>
Aluminum has no magnetic property. There must be something magnetic in
it,too. (???)
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