Calcite

Energy Cleansing / Dispels negativity / Enhances mental growth and spirituality / Promotes mental calmness / Enhances memory / Concentration / Productivity / Useful for studying / Confidence / Determination / Inspiration / Sexuality.

You can program a crystal, which means asking its help with something specific of all that it can offer you. However, this is not mandatory. The crystal will help you anyway where the universe deems you need reinforcement or assistance. Basic condition of course is that you value it and believe in its power.