Why is it said that a broken mirror brings bad luck? Why
It is likely that this belief is linked to the strong symbolism of the mirror: "magic" that can duplicate things, but even people. This feature can have led previous generations to think that breaking a mirror image in some way tantamount to killing the person himself or to hurt a bit 'as it is in voodoo rituals, when the witches tortured with pins is a doll that is the unfortunate recipient of the unfortunate influence.
Like all surfaces capable of reflecting the images (glass, water, metal), since ancient times been regarded as the mirror is full of magical powers. The Romans thought that it would allow to observe everything that happened in the more distant parts of the empire. Religions such as Islam or Judaism, however, advise you to flip the mirrors during the wake, so that they prevent the soul of the deceased to leave the mundane world.
The mirror is also present in the practice of witchcraft, real or fantastic: Catherine de 'Medici God through a mirror magic, and the wicked queen in Snow White's submitted every day's famous question: "Mirror, mirror on the wall Who's the fairest of them all? "
source: focus.it