Yes, dried flowers and crystals can be used in candles. However, the wick must be the only combustible item in the candle at all times. If the flowers and/or crystals become combustible then this is not an accepted risk to the Insurer. You can read more on this here.  The candle connoisseurs at Lemon Canary sum up the answer perfectly in this blog post. Have a read if you would like some guidance to ensure your beautiful candles comply