It is fairly easy to grow your own crystal at home from lots of different substances and preserve it indefinitely. In the picture below, the Borax crystal is forming on a pipe cleaner in the shape of a snowflake. The pipe cleaner can be any shape and color, and you can even add food coloring. Borax crystals grow well on something submerged, as shown. Salt crystals, on the other hand, grow better from the bottom up (the salt crystal projects below are both Christmas tree shapes). Crystals are great projects for all ages and make great ornaments and sun catchers!
Crystals are forms of solid matter that have ordered structures. Crystals often appear in a clearly geometric shape and many familiar things are crystals, including diamonds, graphite, salt, sugar, caffeine, and snow. Follow this link, or any other link in this post, for some information about crystals for kids.
Borax is a naturally occurring substance that is great for cleaning and for growing your own crystals. Here are two links to Borax crystal projects:
You can also grow crystals using salt and bluing:
Here is a glow in the dark crystal project using Alum:
And, you can grow a sugar crystal and EAT it: