Which of these crystals is better?

I personally suggest amethyst, because you are still a student, so I think amethyst is more suitable!

Wearing amethyst jewelry helps to calm the playful mentality, develop wisdom, strengthen memory and attention, study hard and enhance exam luck.

White crystal can increase human energy, enhance eyesight and absorb radiation best! White crystal can increase concentration and enhance memory, and candidates wear it obviously. So white crystal can also be good. Can be used as a second choice.

Powder crystal is mainly to strengthen the heart and lung function, promote the health of circulatory system and respiratory organs, relax tension, relieve irritability, and broaden your mind. Therefore, powder crystal has an absolute value-added effect on interpersonal relationship, love and strengthening its own charm.

Tea crystal is helpful for calming the nerves, stabilizing emotions, improving sleep, expelling pathogenic factors in the body, relieving fatigue, enhancing human immune function, activating human cells, promoting the development of regenerative ability, slowing down aging and restoring vitality. Women often wear it, which can regulate gynecological diseases and endocrine. It is the best choice for healthy crystal.

Red agate can strengthen blood circulation, regulate qi and blood, treat gynecological symptoms, stop menstrual pain, promote metabolism, and has beauty beauty effect on skin.

I'll tell you everything else. I hope you can find the right one! Good luck!