All gemstones are receptors and take on the influences around them, whatever these may be. They reflect and hold the strongest energy that they are exposed to. Gemstones of sensitive or mutable planets, like the Moon and Mercury, are more susceptible in this regard.
All gems need, first of all, an initial purification to clear out such influences. This cleanses them of any impurities that may have attended their production or their sale. Purification is more important if the gem was previously worn by another person as gems will absorb much from a person over time.
Certain substances in nature have the power to clear negative influences from gems. Water is the most basic. Immersing a gem in ocean water or in water from a mountain stream is good. Soaking a gem overnight in a copper vessel filled with pure water is another method. Water from silver and gold vessels is yet stronger. Special Ayurvedic nervine herbs like tulsi (holy basil), brahmi (gotu kola), calamus, sandalwood or small amounts of camphor are particularly useful for making gems receptive to higher influences. Small amounts of these herbs can be added to the water used to purify gemstones.
Another simple method is to soak gems overnight in raw milk, which has a strong absorptive property itself. More preferable is a fivefold mixture of raw milk, yogurt, ghee (clarified butter), honey and raw sugar. This mixture is particularly useful for opaque stones like pearl or red coral.
One can also use internal methods, like clearing a stone through meditation; focusing ones awareness on the stone while allowing the mind to come to a state of complete calm and rest. It is good to chant the appropriate mantra for the planet as well, meditating on the planetary deity. We should meditate upon the gem as located in the heart chakra, third eye or on top of the head, wherever we want its higher influences to manifest.
Gems can be taken to temples or other holy places and blessed by spiritual teachers. They can be empowered through planetary rituals like pujas and yajnas. In short, gems should be treated as sacred objects. They should not be looked upon as mere possessions or ornaments but as tools of bringing our lives in harmony with the greater powers of the universe.
Gemstones should be purified the evening before one chooses to put them on. One should rise before dawn on the appropriate day, perform a morning meditation and then put on the stone at the time of sunrise, repeating the appropriate planetary mantra at least 108 times, while meditating on the planetary deity.