Start with making a chrome sphere.
Fig. 1

Now select the Rectangular Marquee Tool and make a selection similar to fig. 2. (It's easier if you use the zoom-in option 1-2 times).
Fig. 2

Now fill the selection with 60% black (Edit - Fill). Keep your selection and use your arrow keys to move the selection 2 picels down. (Hit the "down arrow" 2 times).
Fill the selection with 100% white.
Now move your selection up 2 pixels an fill the selection with 60% black.
Deselect and your finished!