greisen
/ˈɡrʌɪz(ə)n
/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.A greisen is a quartz - mica aggregate containing significant amounts of cassiterite, wolframite, fluorite, topaz, rutile, and tourmaline....
- It has been collected in a road cut near Grant Mills, Cumberland, Rhode Island; in Stratford, Fairfield County, Connecticut; and in greisen with purple fluorite at Irish Creek, Rockbridge County, Virginia.
- Eventually we reached the site, a few trenches along veins of greisen.
Origin
Late 19th century: from German, probably a dialect word, from greis 'grey with age'.