Grouwacke or Grauwacke: How To spell?

The word Grouwacke is misspelled against Grauwacke, a noun meaning "Graywacke."

Word contains consecutive vowels 'AU' in between alphabets gr & wacke is misspelled as 'OU'
Wrong Spelling:  gr-ou-wacke 
Correct Spelling:  gr-au-wacke 
Check more misspelled words of Grauwacke to spell it correct.

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