These are some of the cheaper, and more reliable crystals that I have grown. Alum is available at many stores as it is used for pickling. However, it will grow beautiful crystals when dissolved. I have noticed that alum likes to grow large crystals when conditions are right. Were-as other types may want to form small clumps or towers.
The step by step walkthrough can be found here. This website shows many different types of crystals to grow, and also the information on how to do so. With the alum crystals, they have grown clear ones, and cut them like a gem. I have not gotten any like this yet, but I have not set up a way to slowly cool the crystal solution yet.
Using a Rock
My favorite are these. I placed a rock in the solution to get the crystals to grow on it instead of growing the crystals by themselves. They look more natural this way. Almost like they were grown in nature.
Large Single Crystals
Throughout the many times I have grown with alum, I have gotten a few different results. Optimally, I like to get results like these.
Smaller Single Crystals
I have ended up with several single crystals, but they are small this time. I had to use a different growing container for these, and so I am thinking it was that.
After a while, you will find the best ways to grow the alum crystals. In general though, the slower the solution cools down, the bigger the crystals will end up being.