The last and highest rank of coal is anthracite. Unlike the other types of coal, this high-energy coal is hard and black, burning with little smoke. As different types of coal are used in different applications, varying processes and process engineering are required.
Copper is a common treatment for rheumatoid arthritis and osteoporosis because it helps promote healthy collagen in the body, copper may relieve aching joints and minimize loss in mineral bone density. An old folk remedy for arthritis calls for wearing a copper bracelet to reduce pain and inflammation.
The health benefits of copper jewelry, or for that matter, jewelry in general, has always seemed a bit far-fetched to me. Of course, I am not a scientist and haven't researched the subject extensively, but it seems that whatever trace amount of copper could be absorbed by the skin couldn't be that powerful.