silica is indeed a composite of glass and comes from 5 natually found elements including quartz, cristobalite, tridymite etc.
the issue is knowing if silica wick is amorphous or crystalline ( amoprhous wick is made from glass substrate, crystalline from naturally occurring fibre however it is crtyslline which is in fact the cause of silicosis though the effects require substantial amounts of silica to be inhaled through air and the like over 20-30 years or more and dont think that would be an issue with vaping as the silica is "dampened down" by the juice so any particle inhalation would be negligable.)
having just done some checking it does appear the wicks are amorphous ( glass fibre based so harmless in terms of silicosis
as silica ( amoprhous ) is a man made fibre extensive research going back many decades confirms that amorphous silica breaks down and dissolves in the body and has no negative effects unlike crystalline silica which can among other things result if exposed to significant amounts ( millions of times more than any wicks you will ever use) can result in silicosis and asbestosis in certain forms of crystalline silica.
to summarize
1. It is amorphous not crystalline.
2. amorphous fibres are too large to inhale past the throat.
3. If you got some in your mouth you would just spit it out or swallow it.
4. Silica fiber undergos dissolution and transverse breakage due to amorphous structure.
a fiber is a particle that has a length ≥5 µm and a length:diameter ratio (aspect ratio) of ≥3:1 or ≥5:1
silica in ecigs has a particle density of between 20 and 35 µm so therefore not actually classified as being able to create particles