What is a mojo stone?
The simple answer is, it's a stone charged with good mojo.
It's kinda hard to describe mojo because you can't see or hear it. Instead you feel it. You felt the mojo resonate with your own when you picked out your stone. Like those before you who found, cut, and polished the stone, you found something you liked about the stone.
An object that is loved emanates good mojo. It's like a battery that stores good vibes. Not only was this stone brought to a vortex of life and peace (my backyard in Arizona), it was shaped and polished with great joy. Chances are you felt a connection with the stone you have, and can now feed off the energy it possesses. As you do good in the world your mojo stone re-charges.
Are there stones with bad mojo?
Unfortunately, yes, there are stones with bad mojo. These are the cheap stones purchased in bulk that come from countries like China where slave labor is used to mass produce cabochons and jewelry. Many workers in poor countries die early from silicosis, which is caused by grinding rocks dry and inhaling the dust. Any stone polished under duress of any sort will possess bad mojo.