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Not all, some of them are expensive, but important is to have a genuine source because these days even the not costly crystals are sold fake because of the huge demand.
Crystal healing is a complimentary therapy, it basically helps clear the energies which in-turn will boost the healing process and whatever treatments are being done will work at best.
But there are many subtle ways in which the crystal works on the mind and one starts seeing progress over a period of time in their overall mental and emotional health as it helps in stabilizing both of them.