The word Grawacke is misspelled against Grauwacke, a noun meaning "Graywacke."
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Word contains consecutive vowels 'AU' in between alphabets gr & wacke is misspelled as 'A' as letter 'U' is phonetically ignore
Wrong Spelling:  gr-a-wacke 
Correct Spelling:  gr-au-wacke 
Explore spell check of Grauwacke to spell without errors.