Yes, dried flowers and crystals can be used in Candles. However, at all times the wick must be the only combustible item in the candle. If the flowers and/or crystals become combustible then this is not an acceptable risk to our Insurers.
This is why it is important that you ensure you batch-test your products consistently so that you ensure your products are safe for consumers.
Please refer to ACCC for more information on PRODUCT SAFETY.