greisenPronunciation: /ˈgrʌɪz(ə)n/Definition of greisen noun [mass noun] Geology a light-coloured rock containing quartz, mica, and fluorine-rich minerals, resulting from the alteration of granite by hot vapour from magma. Origin: late 19th century: from German, probably a dialect word, from greis 'grey with age'greisen in other Oxford dictionaries Definition of greisen in the US English dictionary
