The fact that some practitioners of New Age thinking have adopted crystals as objects through which evil can manifest its power does not make crystals themselves evil. God has created all things for us to enjoy, and crystal can make beautiful jewelry (see 1 Timothy 6:17). Many believers see the beauty and order of crystals pointing to a beautiful God who created the universe with a marvelous order.
If, however, you have been using crystals as "power objects," it may be advisable for you to follow the practice of the Ephesian believers in Acts 19:18-20 and remove any bridges the enemy could use to get back into your life. If you are unsure about what to do, simply ask God for wisdom, determining ahead of time that you will trust His guidance as He makes His will for you clear (see James 1:5-8).