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These inclusions in tourmaline are called growth tubes. They might contain liquid or they might be hollow. Do you think this looks like a garden scene? - Photo by John I. Koivula/GIA
The small dark circles in this tourmaline are gas bubbles inside liquid inclusions.
This is a magnified view of a type of tourmaline. The gem contains a tourmaline inclusion that looks like a colorful twig. - Photo by John I. Koivula/GIA