Approximately 1"
Fire agate is the stone of passion. It helps to light a spark within you so it is great for any project that requires a lot of energy and gusto. It is also good if you are feeling a bit sluggish, try holding a piece instead of going for a second cup of coffee. It helps restore vitality.
It is a very sensual stone and can help stir up a little romance.
Is someone sending negative energy your direction? Fire Agate will reverse that and send it back to the one directing it towards you.