Gneisic or Gneissic: How To spell?
The word Gneisic is misspelled against Gneissic, an adjective meaning "Relating to, or resembling, gneiss; consisting of gneiss."
Gneissic has double "ss" is mispronounced as "s"Remember double 'SS' in between the strings gnei & ic which should not be misspelled with single 'S'
Wrong Spelling:  gnei-s-ic  Correct Spelling:  gnei-ss-ic 
Find more wrongly spelled words of Gneissic to spell it well.