Let's talk about the scientific mechanism involved behind the functioning of the Gemstones. In simple language, how do these Gemstones actually work. We will have a look at this concept right from the birth of a human. As most of you people may be knowing that out of the 12 Signs there is always a Sign rising at a particular degree any particular date, time and place. This Sign is called Ascendant or Lagna. When a child first comes out of his mother, the particular sign rising at that time in the sky as well all the planets where ever they are situated in transit at that time, all of them Register their positive or negative impacts on the new born. The Sign rising at that time is called the Ascendant of the native which becomes First House of the Horoscope and all the planets are arranged in different houses of the Horoscope according to their transit position at the time of the birth of a child.
      To have a scientific look at this concept, all the twelve houses of the Horoscope may be considered as 12 energy points in human body which register, store and emit energies. This way at the time of birth of a native, some energy centers register negative energies and some energy centers register positive energies. While some energy centers do not register any energy at all. It simply means that some house of the Horoscope have good and bad planets or we can say positive and negative planets while some houses of the Horoscope may be completely empty. Depending upon the nature of these energies the planets function or work as good or bad planets for a particular native. Again depending upon the degree and placement of a particular planet in a particular energy center, the planet may be strong or weak, clean or afflicted. This is where Gemstones plays a vital role.
       If a planet has registered positive energy at the time of the birth of a native, it becomes a good planet for that particular native and an expert Astrologer can read it from his Horoscope. But if due to its placement, affliction or some other concept, it has become weak, it would simply mean that the planet will remain good for the native but will not give its proper results as it is weak. So in this case wearing a Gemstone for that particular planet is prescribed to give energy to the weak but good and positive planet after analyzing the Horoscope.
    All the Gemstones work on the principle of absorption and transmission of some particular wavelengths which belong to some particular  planet. For example a Ruby (Manik) will absorb and transmit Sun's particular energy to the body of the wearer. And if the Sun is good but weak for that native, it will gain energy and become strong and it will boost the results given by it to that particular native. Same is the case with all other planets. This is the reason why Gemstones are prescribed. But it should be noted carefully that if a planet is negative for a native, wearing the Gemstone of that planet will transmit more power to that planet which being negative in nature will become more deadly. So Gemstones can only increase the power of a particular planet in your Horoscope or in your body but they can not change the functional nature of that particular planet in your Horoscope or in your Body. There are also some planets in some horoscopes which are giving most of the positive results to the native with some negative effects or side effects & on the other hand there are some planets in some horoscopes which are giving most of the negative results with some positive results. For example a particular gemstone may give you good results with your profession but at the same time it may cause problems in your married life. A gemstone may bless you with good health and long life but at the same time you may suffer financial losses. So which gemstone should be worn for what purpose, without any side effects, and what period of your life is good for wearing a particular gemstone is a matter of expertise and experience.  That is why Gemstones should be worn only on the advice of an expert Astrologer who knows a great deal about Gemstones and their applications. Wearing the right Gemstones can bless you with very good results where as whereas wearing the wrong Gemstones can bring great misfortunes to you.Om Namah Shivaay!