Natural Fiber Optic Conduit: a special crystalline form of the mineral gypsum acts as a natural fiber optic image conduit in this square cut specimen with polished ends. Morocco seems to be the main source of this fibrous form, called satin spar gypsum, which exhibits pearl like luster and chatoyancy along two axes and transparency along the direction of the fibers. Each natural crystal microfiber extends the length of the rod and acts like a man made glass fiber where the index of refraction is

Story of Submarine cables, Fiber optic... - Solaiman Shukhon