Our rock candles are oil candles that burn ultra-pure paraffin oil (available at craft stores.) We use fiberglass wicks that will last indefinitely. There is no smoke or scent (although you may add scented oil if you wish). Citronella oil may be added if using outdoors for bug control. To refill the candle, remove the wick and put the small funnel we provide in the hole and fill it up, replace the wick and you’re good to go!Theserock candles are made of slate rock with gray, brown, black and green hues.