First, it's important to understand the primary purpose of the crystal you are wearing. If it's for attracting wealth, enhancing luck, or improving relationships, such as Golden Rutilated Quartz, Green Phantom Quartz, Strawberry Quartz, or Rose Quartz, it should be wear on the left hand. If it's for warding off evil or protection, such as Obsidian or Black Rutilated Quartz, then it should be wear on the right hand. If the crystal serves both purposes, you can wear it on either hand, but wearing it on the left hand is preferable.