In gemological field there is no precious or semi-precious name. These name were created in trade (way-back) to separate higher priced gemstones from lower priced ones and all gemstomes have different chemical composition & property so they might do differently in astrological sense but the alternatives that I provided are the best ones in case of prices.
As far as I know, it is the light/rays that transmit/reflects from the gemstone to the body matters. And, when someone says that after some time gemstone energy or power degrades it basically means that the gemstone was not cleaned and got dirty and lights could not be reflected or transmitted well from it. So, it is advised to clean gemstones on regular basis so that its refraction/reflection gets properly to the body and surrondings.