Very lovely rainbow aura quartz geode that measures about 9cm x 6.5cm.
Aura quartz is a natural quartz crystal that has been permanently treated either by fusing titanium and niobium to it in a vaccuum or sometimes the colours come from a dye that has been fused to the surface of the quartz in a similar way.
Please be aware that these lovely geodes initially can leave a bit of dust on the fingers.