malthacite
/ˈmalθəsʌɪt/(also malthazite) Mineralogy. Now historical
noun
A white or yellowish clay similar to fuller's earth, usually occurring as scales.
Origin
Mid 19th century; earliest use found in Henry Watts (1815–1884), chemist. From German Malthacit from ancient Greek μαλθακός soft + German -it.