Quartz crystal is probably the best thing, but clean good quality sand, water, oil, other gems, silver, copper and gold are also fine, and many people also like holographic stickers. For example, LifeWave’s X39 stickers (Introduce the Light Therapy of LifeWave’s X39 Sticker), and also Energy Wave Ltd has many different types of wearable frequency products designed to improve your health, such as energy bands, patches, shields, cards, crystal pendants, etc (Introduce Energy Wave Company’s Energy Products). It depends on what you are doing what and how you want/need to use it.
