Stones are prescribed for debilitated planets. They should be propitiated properly and worn in the right hand. A friend of mine bought topaz and wore it in his left-hand in spite of advice from me to wear it on his right hand. With in a few days the poor girl's vehicle had an accident and her factory got raided. Forget any great results if the gem is worn without pooja and at an auspicious time.
Gems can become diabolic.
A particular weight is also prescribed. If you know all these criteria then go ahead with the gems. It will work and I have heard great results. Be careful of the racket of Nadi astrologers who exploit in the name of Dana that will enrich their pocket. I am not telling all of them are like that.