Many of the semi-precious stones you can benefit from are found in the typical craft store in your local strip mall. We have two craft stores in our area- Micheal's and Joanne Fabrics.
You can find Garnet, Tiger's Eye, Howlite, Quartz Crystal, Hematite, Malachite, Yellow Jade, New Jade, Carnelian, Soladite, Rhodonite, Red or light brown jasper (called "Picture Jasper") Rose quartz, Amythest, Smoky Quartz, Unakite, and other semi-precious stones all polished in round or rectangle beads- or in polished chips.
I know that one member posted how he has more luck with expensive stones over cheap stones- but now the more that I think of it-- nothing that God created is ever wasted in Nature. EVERY stone has some property involved with it besides taking up space in the ground.
This is the Creator's Way of Effeciency and Harmony. Not only does everything created have a type of extra-ordinary beauty to it when it is polished or pruned, or cultivated (think pruned rose bush), but nothing is ever wasted in Nature. It has multi-purposes and enriches not only the Earth itself and the Earth's Electrical magnetic field, but everything created affects everything else created.
Just as they say "No man is an Island to himself" , so to in Nature, everything has an influence on other created things. This applies to the human body and our own energy field as well.
I feel that as the Sun energizes life and all living things need Light (Just as we all need God) Each stones inherit potentials will benefit by having been exposed daily in the Sunlight to cleanse and energize them. Nothing beats the Suns energy except God, Himself.