Gneisoid or Gneissoid: How To spell?
The word Gneisoid is misspelled against Gneissoid, an adjective meaning "Resembling gneiss; having some of the characteristics of gneiss; -- applied to rocks of an intermediate character between granite and gneiss, or mica slate and gneiss."
Gneissoid has double "ss" is mispronounced as "s"Remember double 'SS' in between the strings gnei & oid which should not be misspelled with single 'S'
Wrong Spelling:  gnei-s-oid  Correct Spelling:  gnei-ss-oid 
Find more incorrect spellings of Gneissoid to spell right way.