Raw Pyrite For Memory and concentration. Also known as fools gold.
Pyrite Fools Gold - Its golden colour associates it with gold. Some people always this this is gold so it is also known as "Fool's Gold". The resemblance of pyrite to gold has made it the symbol of money and good luck. The stone makes a wonderful energy shield, blocking out negativity from various sources.
Price is per crystal/bag. Photo is a guide.
Disclosure: If you're worried about your health always see your doctor first. There are no guarantees with crystals, but they may enhance your life.