Crystals are treasures of the Earth. They have ancient heritage and incredible energies within.
There are many many different forms of crystals and it pays to do your research on what might be a good match for you where you are at. Also walking into a crystal store and taking not of what you may feel and energetic pull towards. Sometimes the crystal chooses you.
Is it safe to have crystals and flowers in candles?
In a short answer. YES it is safe. It is safe it they are placed correctly. When I pour my candles I try to add the botanics (and from here on out I will be extra conscious) in already melted wax so that when you light your wick the flame does not ignite the botanics. It is more likely to just melt and drift to the bottom of the jar as the wax melts.