When to be careful wearing a gem for the Mars

Gems for Mars should not be worn when there is fever, infection, bleeding, ulcers, or excessive sexual drive (high Pitta). Psychological factors are anger, conflict, argument, too willful or impulsive a character, an aggressive, wrathful or martial disposition.

Astrological factors are mars as a malefic lord (particularly for Gemini and Virgo ascendants), or Mars in conjunction with benefics we may want to strengthen (like the Moon, Mercury and Venus). Generally we should avoid gems for Mars if it is in the seventh house, or if it is strongly disposed in angles.