Article 810 or the NEC calls for #10 AWG copper as the smallest diameter conductor to be used to connect the mast to your existing electrical service ground. The connection between your coax grounding block and electrical service ground is a separate connection and is also to be at least #10 AWG copper. (The NEC does provide for some alternates to copper, but copper is going to be corrosion resistant and easier to obtain for most folks.)
The conductor can be solid or stranded, insulated or bare.
If you add a ground rod, the minimum conductor for bonding it to your existing electrical service ground system is #6AWG (which is larger in diameter than #10).
Connections to ground rods should be done with a connector that is rated for 'Direct Burial'. These are usually bronze, very corrosion resistant, and have strength similar to many grades of steel. The big box home centers are usually stocked with such parts and materials.
See:
http://forum.tvfool.com/showthread.php?t=901 (post #20 is a summary)