Black tourmaline is a gemstone i have spoken about in great detail in my group on facebook and a video dedicated to it on youtube. Its the most protective of the gemstone world. Its excellent for all types of protection from home to person, is very groudning, has been used by crystal healers to aid pain relief for many years and creates a shield around your energy field or that of your home/altar.
To make a generator like this you need very high quality raw tourmaline, the low grade with the striations just wont do. These are polished inline with their natural shape, facets and points. The carving done is simply to create a flat bottom.