Grisen or Greisen: How To spell?

The word Grisen is misspelled against Greisen, a noun meaning "A crystalline rock consisting of quarts and mica, common in the tin regions of Cornwall and Saxony."

Word contains consecutive vowels 'EI' in between alphabets gr & sen is misspelled as 'I' as letter 'E' is phonetically ignored
Wrong Spelling:  gr-i-sen 
Correct Spelling:  gr-ei-sen 
Find more wrongly spelled words of Greisen to spell it well.