In theory along with considerations Mr. JVS Rao mentioned, its important to take into account purpose for wearing stone as well (health, mental peace, career or marriage).
Practical experience says that wearing stone is more from optics point of view and it cannot replace hard-work, meditation and self discipline. Otherwise everyone could wear stones and improve their situation (job/marriage/education) which is not the case.
God Bless you with logic and rationality,
Astrologer Deepak