Greasen or Greisen: How To spell?

The word Greasen 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 'EA'
Wrong Spelling:  gr-ea-sen 
Correct Spelling:  gr-ei-sen 
Explore spell check of Greisen to spell without errors.