Citrine Geode Flat BottomA hollow lined with goldthe stone reveals itself only when opened. Citrine geodes begin as gas cavities in volcanic rock. Over millions of years, silica rich groundwater seeps in and deposits successive quartz layers inward, building the crystal points you see here. Heatwhether from later geological activity or, in most commercial material, from slow kiln heating to 400500Cshifts the iron chemistry in amethyst toward citrine's warm amber. The flat