unpolished stalactite agate.

agate brown cave cavity chalcedony collector color concentric crystal crystalline crystals decoration decorators field gemmology gemology gems gemstone genesis healing layer material mineral mineralogy minerals natural nature nodule ornament ornamental oxide popular precious pseudomorph quartz rock rocks rough semi silica siliceous sio2 stalacmite stalactite stalactitelike stalactitic stone stones talisman treasure uncut unfaceted unpolished valuable value