Before wearing a gem one should have their Vedic horoscope checked by an expert astrologer to determine which planets are well-placed.
By Richard Shaw Brown,
Gemologist (GIA).
According to Vedic culture gems are believed to resonate with the same piezoelectric impulses as their ruling planets. Therefore we should only wear gems for planets which are well-placed or anukul in our Vedic horoscope.
Anukula means a planet that is beneficially disposed either by being strong in own sign, good house, ruler of houses which will bring positive results, or otherwise not malefically disposed nor inclined to produce evil influence. A planet which is good for the chart either naturally or by house rulership, yet somewhat weakened by placement may be strengthened through the gem, or a planet which already is strong and giving benefic influence may be further strengthened for gains in particular areas of life by wearing the gem.
Based on this simple premise we list below basic guidelines on how fine quality jyotish gems might influence us according to our horoscope.

The influence will be toward nobility, dignity, power, leadership, and confidence. One will be well-read, pious, strong, compassionate, and untroubled.

The influence will be toward sensitivity, good habits, stability, and health. One will be wealthy, industrious, and respected.

The influence will be toward humanitarianism, spiritualism, optimism, faith, and good judgement. One will be powerful, respected, and a leader of men, although susceptible to anger.

The influence will be toward originality, inspiration, insight, and uniqueness. One will be exotic, wealthy and fortunate.

The influence will be toward rationality, wit, skilfulness, and dexterity. One will be educated, happy, fortunate, and highly respected.

The influence will be toward attractiveness, grace, elegance, and longevity. One will be refined, humanitarian, and possess many positive qualities.

The influence will be toward spiritualism, intuition, universality, subtleness, and sensitivity. One will be wealthy and protected from evil.

The influence will be toward discipline, responsibility, realism, durability, and humility. One will be long-lived, charitable, proficient, and an affectionate mate.

The influence will be toward positive energy, strength, courage, passion, and aggression. One will be active, have great energy, be learned, well known and regal.
So before wearing a gem one should have their Vedic horoscope checked by an expert astrologer to determine which planets are well-placed.