phenakite
/ˈfiːnəkʌɪt/ /ˈfɛnəkʌɪt/(also phenacite) Mineralogy
noun
A rare mineral of the trigonal system consisting of beryllium silicate, Be2SiO4, and occurring as colourless or white scales and prisms.
Origin
Mid 19th century; earliest use found in London and Edinburgh Philosophical Magazine. From German Phenakit from ancient Greek ϕένακ-, ϕέναξ cheat (of uncertain origin: see note) + German -it, so called on account of its having been mistaken for quartz.