Kbase Article of the Week: iBook — White Greasy Substance in Battery Bay →

Apple Support:

If you see a white, greasy substance in the computer’s battery bay, frequently near the battery electrical contact points, it is no cause of concern. The substance is merely a non-harmful grease that is applied during production of the iBook computer.

The grease is applied to the springs in the battery bay to help ease removal of the battery.

If there is excessive grease, you can remove it with a clean, dry, lint-free cloth.

Note: While the grease does not represent any potential harm if it comes in contact with the your skin, it should be washed off using soap and warm water.