These crystals grow naturally in caves. They don't actually glow - bioluminescent organisms feed on them and emit light. Also heat - be careful!
Golden Cave Crystal price in Growtopia: sells for about 5 WL (median of 27 offers from community Discords, past 30 days). Live price chart and the latest buy and sell offers.
Recently sold at: VUWKP, KQCOT, FT3W, FT3WAT