rhyacolite
/rʌɪˈakəlʌɪt/Mineralogy. Now historical and rare
noun
A feldspar occurring chiefly as white or colourless crystals in volcanic rocks, subsequently identified with sanidine.
Origin
Mid 19th century. From German Ryakolith from ancient Greek ῥυακ-, ῥύαξ mountain-stream, lava-stream + German -o- + -lith, with remodelling of the ending after -lite.