boti national geographic kristal laten groeien set purple 1The National Geographic Purple Crystal Growing Lab is an easy and fun way to grow a crystal at home! Simply mix the crystal growing powder with water, add your seed stone, and in just a few days youll have an amazing crystal! Easy to follow instructions and a colorful learning guide are included. 1 Sachet Purple Crystal Growing Powder (3. 35 oz 95 g) 1 Seed Stone 1 Learning Guide with instructions.